The Lord visited Sarah as he had said, and the Lord did to Sarah as he had promised. 2 And Sarah conceived and bore Abraham a son in his old age at the time of which God had spoken to him. 3 Abraham called the name of his son who was born to him, whom Sarah bore him, Isaac. 4 And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. 5 Abraham was a hundred years old when his son Isaac was born to him. 6 And Sarah said, “God has made laughter for me; everyone who hears will laugh over me.” 7 And she said, “Who would have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age.”
8 And the child grew and was weaned. And Abraham made a great feast on the day that Isaac was weaned. 9 But Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, laughing. 10 So she said to Abraham, “Cast out this slave woman with her son, for the son of this slave woman shall not be heir with my son Isaac.” 11 And the thing was very displeasing to Abraham on account of his son. 12 But God said to Abraham, “Be not displeased because of the boy and because of your slave woman. Whatever Sarah says to you, do as she tells you, for through Isaac shall your offspring be named. 13 And I will make a nation of the son of the slave woman also, because he is your offspring.” 14 So Abraham rose early in the morning and took bread and a skin of water and gave it to Hagar, putting it on her shoulder, along with the child, and sent her away. And she departed and wandered in the wilderness of Beersheba. 
Last week we watched Father Abraham resort to the same horrible sin of pimping his wife to a king for his own safety as he had done so many years before in Egypt. He did this shortly after receiving God’s revelation that the Promised Seed would be born to him and Sarah before the year was out. From a human standpoint, Abraham’s distrust made Isaac’s birth impossible. His wife was in Abimelech’s harem. Yet again, God intervened. He closed the wombs of the royal court, so that the king would have no more seed. He kept Abimelech from Sarah and indicted the pagan king in a night vision.
It was Abimelech who held the moral high ground as he confronted God’s backsliding prophet. But, for the sake of his Promised Seed, God preserved Abraham and Sarah’s lives. Abimelech (My Father is God the King) spared them from their deserved execution; showered them with silver, slaves, livestock; and conferred upon them the status of favored citizens in his land. God’s covenant loyalty love did not depend on Abraham and Sarah’s faithfulness or working faith. Though we are faithless, God remains faithful in his steadfast love for his people for the sake of his Promised Seed.
Chapter 21 gives us a scene of domestic life in Camp Abraham as the Promised Seed arrives. This plays out against the international conflict of Abimelech’s seed having been cut off and restored in the previous scene and the land conflict and treaty that closes out this chapter. Again, the themes of land, seed, blessing, conflict and God’s faithfulness reappear.
PROMISED SEED ARRIVES (1-7)
Abraham had been waiting upon God’s fulfillment of the promised seed for 25 long years. Waiting is built into the lives of every person who trusts into the person and work of the Promised Seed. Many of us long for right things like seeing our loved ones saved, or overcoming particular sins, or gaining greater trust into God’s promises. Life with God is a life of waiting. Even the saints in glory (like Abraham and Sarah) are waiting for that great day when they will have their resurrection bodies like Christ’s and walk upon the new sin-free earth under the new heavens. They wait for God’s final judgment and their vindication (Rev. 6:10):
How long, O Lord, holy and true, until You judge and avenge our blood on those who dwell on the earth?” 11 Then a white robe was given to each of them; and it was said to them that they should rest a little while longer, until both the number of their fellow servants and their brethren, who would be killed as they were, was completed.
Isaiah sang, “they who wait for the Lord shall renew their strength; they shall mount up with wings like eagles; they shall run and not be weary; they shall walk and not faint.”  It should be enough for us that we know the One who knows all things, including the “when” of things for which we long. Waiting is an ultimate expression of trust, as we have learned from Abraham and Sarah’s repeated attempts to take control of their own destinies. Again, and again we must re-learn that God is no personal genie who exists for our own wish fulfillment – even when our wishes are biblically acceptable ones. He has decreed all things and the timing of them for his glory and our good.
After months of grim news – such as God’s devastation of the Dead Sea Plain, the sins of the Lot Family, the humiliating sins of the Abraham Family – the time finally came for Abraham and Sarah to see God’s covenant promise of seed fulfilled. “The Lord visited Sarah as he had said, and the Lord did to Sarah as he had promised. 2 And Sarah conceived and bore Abraham a son in his old age at the time of which God had spoken to him. 3 Abraham called the name of his son who was born to him, whom Sarah bore him, Isaac.” After all the misery of sin and judgment comes laughter. The long-awaited nativity is narrated very simply.
The poetic parallelism stresses that God was faithful to his covenant promises. Three times God’s faithfulness is mentioned in these first two verses: “as he said,” “as he promised,” and, “at the time of which God had spoken to him.” God had told Abraham a year earlier that Sarah would bear a son within a year and that he was to name the son “Isaac” (cf. 17: 15-22, esp. v. 21). Abraham had laughed at this revelation with incredulous belief. Sarah laughed too as she overheard a second assertion that she would give birth within a year (cf. 18: 10-15, esp. v. 12). Now, what Abraham and Sarah had only been able to accept by faith in God’s revelation, they could accept by observation. God is faithful to his promises. The joyful 90-year-old nursing mother (the only one in history) and her baby boy open the way for the realization of God’s covenant promises in their fullness – Isaac in type, and Christ in fulfillment.
God is true to his word in judgment. God is true to his word in blessing. He makes good on his word in his time. Jesus said, “truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.” That declaration came from the Promised Seed, who is the “Yes” and “Amen” to all the promises in God’s Word (2 Cor. 1:20) for He himself IS the Word (1 Jn. 1:1). This is the way everyone of God’s elect people is meant to live, with the deepest unshakable trust into God’s revelation. Of course, only Jesus could do that perfectly. You and I must continually confess our lack of trust and seek fresh rest in God’s plan and God’s promises and God’s timing. We must struggle in this present life to live out of the conviction that only Jesus knows what’s best for us.
Abraham returns to living in obedience upon Isaac’s birth. The text is silent about his emotions, stressing only his obedience. As commanded, he names his son Isaac (“May God Smile Upon/Take Joy in Him”). The inside joke for the family recalls both his and his wife’s incredulous laughter at God’s promise (Gen. 17:17-21; 18:13-15). God has the last laugh and Sarah sings a joyful song in response, “God has made laughter for me; everyone who hears will laugh over me.” 7 And she said, “Who would have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age.” In Abraham’s further obedience, Isaac becomes the first newborn child of the covenant to receive its sign and seal of circumcision. His spiritual destiny was different from that of his old half-brother Ishmael who was circumcised at 13.
SEED OF FLESH DEPARTS (8-21)
Isaac’s birth is recorded in only seven verses. The story of Ishmael’s departure is almost twice as long. Isaac’s name appears three times in this chapter. Ishmael’s name does not appear even once. By verse 8 we know that at least three years have passed since Isaac was born. That appears to be the traditional time for weaning a child (1 Sam. 1:23ff.). Isaac was a toddler and Ishmael is now about 16 years old. Abraham and Sarah throw a feast for Camp Abraham to celebrate the fact that their promised seed has passed through his most vulnerable years in health.
But Ishmael is not amused. You might be reading an ESV and wonder why seeing Ishmael “laughing” was so troubling. It is the same root word as Abraham and Sarah’s laughter; but it’s a different stem. Derek Kidner writes, “it should be translated mocking (AV, RV). This is the intensive form of Isaac’s name-verb ‘to laugh’, its malicious sense here demanded by the context … RSV itself renders it ‘jesting’ (19:14) and ‘to insult’ (39:14, 17). The Apostle Paul wrote in Galatians 4:29 that Ishmael “who was born according to the flesh persecuted him who was born according to the Spirit.”
This is the seed of the flesh rejecting and mocking the Promised Seed. It’s not mere contempt or jealousy that moves Sarah to demand his expulsion. God is using Sarah’s sin to distinguish the heir of the promise from the heir of the flesh. Ishmael has not trusted into God’s saving covenant. Consequently, he hates the Promised Seed as much as the world, the flesh, and the devil hate Christ. It’s the exclusivity of this way of salvation that Ishmael finds so insulting. He, like Cain before him, is the firstborn and beloved of his father. Who is this god of Abraham who chooses a toddler over the firstborn? Ishmael wants no part of the celebration of Isaac as the exclusive salvation of humanity. Yet, Messiah Jesus would declare:
I am the way, and the truth, and the life. No one comes to the Father except through me. 7 If you had known me, you would have known my Father also. From now on you do know him and have seen him. 
As long as Hagar remained a slave, Ishmael had inheritance rights along with Isaac. But once Hagar was freed, Ishmael would lose his right to inherit from Father Abraham. Sarah’s demand to expel Hagar and Ishmael from any share in the inheritance is based on both moral and legal grounds. And, as Paul later explains, ultimately it is based on theological grounds:
30 But what does the Scripture say? “Cast out the slave woman and her son, for the son of the slave woman shall not inherit with the son of the free woman.” 31 So, brothers, we are not children of the slave but of the free woman. 
Abraham was naturally distressed over this family strife. Ishmael had been his pride and joy for 16 years. He had begged God to assign Ishmael the title of Promised Seed (17:18). But Abraham is being called to renounce his sin. And, he is suffering the consequences of it. What heartache for this father to cast away his son! “12 But God said to Abraham, ‘Be not displeased because of the boy and because of your slave woman. Whatever Sarah says to you, do as she tells you, for through Isaac shall your offspring be named. 13 And I will make a nation of the son of the slave woman also, because he is your offspring.’”
This is yet another example of God weaving the tangled threads of sinful consequences into the beautiful tapestry of his glory, overruling everything for good. Later in Genesis, Joseph would come to realize and proclaim of his family strife and miserable treatment, “you meant evil against me, but God meant it for good.” Without God allowing us to suffer the consequences of our sins, we would live even more faithlessly than we so often do, people with no depth or substance; people of shallow trust. God works in sins consequences to grow and mature our trust.
Early the next morning only Abraham showed up to bid a miserable farewell to his now-freed concubine and the spoiled rebellious seed of his flesh. With bread and water, he sent them off to wander in the desert, trusting God’s promise that Ishmael would become a great nation. So, when the water was spent and Ishmael lay dying under the barest desert scrub, when Hagar had given up all hope, God heard the cries of the fleshly seed and extended his hand of common mercy for the sake of his friend Abraham (vv. 17-18). God spoke, directing Hagar to a nearby well and promising her son would become a great nation (v. 18). God promised to be with Ishmael (v. 20).
Bruce Waltke writes of this section:
“Abraham’s natural and supernatural seed both experience God’s testing and blessing. Hagar and Ishmael’s rugged trek has striking parallels to the challenge Abraham and Isaac will have to face: (1) journey into the unknown at the command of the Lord; (2) provision for the journey; (3) child at the point of death; (4) intervention of God’s messenger; (5) parent’s sighting of the way out; and (6) promise of future blessing. Abraham must relinquish his natural seed in order to embrace God’s supernatural promises. Yet even as God initiates an extraordinary future for the supernatural seed, he directs the destiny of the natural seed.”
Though heart wrenching for Father Abraham, Ishmael’s separation from the infant Church and its Promised Seed left Isaac free to inherit the promise of the land and free to pursue relationship with the God who promised himself to his elect people. From Abraham’s fleshly union with Hagar would come a nation of 12 princes to oppose Israel. From Abraham’s spiritual union would come the 12 tribes of Jacob/Israel. Ishmael received God’s common mercy. Abraham, Sarah, and Isaac received God’s grace through their God-given trust into the person and work of the coming Promised Seed. All the hopes and dreams of all the characters, all their sins and rebellious attitudes, all their desperations and disappointments were woven into the tapestry of God’s decree for his glory and the good of his people.
BE’ER-SHEBA TREATY (22-34)
Chapter 21 ends with a bookend to Abraham’s relationship with the Philistine King Abimelech. In their first encounter, God’s prophet had utterly disgraced himself with his craven fear and his lies. But over these last four years, Abraham had been blessed by God with a good reputation, earning him Abimelech’s respect:
22 At that time Abimelech and Phicol the commander of his army said to Abraham, “God is with you in all that you do. 23 Now therefore swear to me here by God that you will not deal falsely with me or with my descendants or with my posterity, but as I have dealt kindly with you, so you will deal with me and with the land where you have sojourned.” 24 And Abraham said, “I will swear.”
Reflecting the pagan superstitions of the world, Abimelech assumed that if good things happened to someone, that person must be favored by the gods. If bad things happened, then the gods were displeased. Abraham clearly had the favor of his god, Elohim, since he had experienced a miraculous birth and grown mightier in wealth. “Abraham had now set the “God is with you” standard that would also become that of Isaac (26: 28), Jacob (30: 27), and Joseph (39: 3).” Camp Abraham was now an even greater threat to Abimelech’s kingdom, should he and the Prophet of Elohim quarrel. The peace Abimelech had sought through marriage a few years before, he now proposes through a treaty which Abraham accepts.
To give us some idea of Abraham’s growth in trusting into God, the final scene of the chapter shows us Father Abraham has grown in confidence; not self-confidence but God-confidence. He is no longer afraid of Abimelech and feels free to bring a charge against the king’s servants. He puts the treaty with Abimelech to the test by asserting his property rights to a well. The result was the Treaty of Be’er-Sheba (meaning “Well/Oath of Seven,” for the seven lambs Abraham puts up as a bond). Abimelech acknowledged the well was Abraham’s and, with a royal oath, returned to Gerar. Moses called their agreement “a covenant.” Their verbal agreement was ratified by a formal oath. Water is life. Abraham has secured life for his posterity with this covenant of water.
Moses concludes the story by writing, “33 Abraham planted a tamarisk tree in Beersheba and called there on the name of the Lord, the Everlasting God. 34 And Abraham sojourned many days in the land of the Philistines.”  “Abraham’s first stopping place in Canaan (Shechem) was by a tree (12:6). Later he built an altar by a tree at Mamre (13:18). He lived near trees (14:13), and entertained Yahweh under a tree (18:1). Now he plants a tree.” Trees were significant landmarks in the arid wilderness. Abraham’s planting of the tree was a symbol of fruitfulness and prosperity. It demonstrated his rootedness in the land where he stayed “many days.”
Abimelech referred to Abraham’s God as Elohim, the most basic (generic) name for any ruler or deity in Semitic culture. There’s nothing wrong with the word, Genesis 1:1 opens with, “In the beginning, Elohim….” But Abraham’s personal Arbor Day celebration at Be’er-Sheba calls upon God using God’s covenant name, YHWH, to which he adds the title Everlasting God (el olam) – a name unique in the Bible. Abraham sees God as the only true, lasting thing in his pilgrim life. Abraham will sojourn in Be’er-Sheba for “many days” (“for a while”) But he is still a pilgrim. Yet, he is a pilgrim who has been granted a settled place (see 20:15) by Abimelech, the man whose name means “My Father is God the King.”
Abraham has come to terms with his mortality now that he has been granted his promised seed, Isaac – the Seed of the Spirit. Abraham is a wanderer. Isaac will be a wanderer. God is everlasting. He does not change. His covenant promises do not change. His plans cannot be thwarted. Not even by the potential sacrifice of Isaac will God’s plan faulter. El Olam will bring his Promised Seed through Isaac in his time. So, Paul will write, “For while we were still weak, at the right time Christ died for the ungodly.” This is Abraham’s expansive bedrock theology flowing out of the consequences of his sins and YHWH’s repeated demonstrations of gracious covenant loyalty. This is perhaps the point in Abraham’s story that moved St Author of Hebrews to write:
By faith he went to live in the land of promise, as in a foreign land, living in tents with Isaac and Jacob, heirs with him of the same promise. 10 For he was looking forward to the city that has foundations, whose designer and builder is God.
Faith does not grow in the temperature-controlled green house. It only grows in the unpredictable climates of a life embattled with the world, the flesh, and the devil. Trust grows out of the rich human soil of work and play, love and hate, anger and boredom, fear and heartache, sickness and health, wealth and want. Trust grows out of horrible sins in which we are faithless, and Everlasting God is faithful. When our hearts are turned from stony rejection of God to trust into the perfect life and sacrificial death of the risen and ascended Jesus, the Promised Seed, then God begins the process of pouring repeated mercies into our shakable lives. This makes us more able to thank him for everything, rest in him for everything, and desire to live more and more for his glory. His work, done in his time, never fails.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ge 21:1–14.
 The New King James Version (Nashville: Thomas Nelson, 1982), Re 6:10–11.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Is 40:31.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ge 21:1–3.
 Hughes, 292-293. Kindle Edition.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Mt 5:18.
 Derek Kidner, Genesis: An Introduction and Commentary, vol. 1, Tyndale Old Testament Commentaries (Downers Grove, IL: InterVarsity Press, 1967), 151.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ga 4:29.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Jn 14:6–7.
 Waltke and Fredricks, 294. “In the Lipit-Ishtar law code (ca. 1875 b.c.), a clause stipulates that if a slave bears children and the father then grants freedom to her and her children, ‘the children of the slave shall not divide the estate with the children of their (former) master.’”
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ga 4:30–31.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ge 50:20.
 Waltke and Fredricks, 292.
 Hughes, 296. Kindle Edition.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ge 21:33–34.
 Hamilton, 2:93.
 Hughes, 296. Kindle Edition.
 Waltke and Fredricks, 300.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Ro 5:6.
 The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Heb 11:9–10.