Genesis 21: Redemptive Fulfillment by the Birth of Isaac

Isaac's birth presents gospel conflict through Ishmael's persecution, and Abraham must remain faithful to God.

Chapter Notes


  • Have you ever had to wait a long time for something? Such events create strong memories in our lives.

  • Genesis 21 records events that revolve around three people: Isaac, Ishmael, and Abimelech.


  • vv. 1–7 - the verses record the birth of the long-awaited son. God did what He promised, and Abraham did as he had been commanded, circumcising Isaac at eight days old. The emphasis on Abraham’s “old age” (vv. 2, 7), is to emphasize the miraculous nature of this event. Isaac’s name means “one who rejoices” and so Sarah declares “God hath made me to laugh, so that all that hear will laugh with me” (v. 6).

  • vv. 8–21 - we are told of the weaning celebration, probably when Isaac is around three years old and perhaps eats certain solids for the first time. While most rejoice, one does not. Ishmael is mocking rather than celebrating. It is a form of hostility, cruelty, and jealousy. Keep in mind, Ishmael is around 16 years of age. What would you think of a 16-year-old bullying a 3-year-old? This matter is considered in Galatians 4, where certain Jews are persecuting Gentile Christians. Both reflect different religions; one of works, represented by Ishmael, and the other of grace, represented by Isaac, and the apostle argues you must cast the religion of the flesh out. This is why Sarah’s request to get rid of Ishmael is affirmed by God to Abraham. So from vv. 14–21, Abraham sends Hagar and Ishmael away. God takes care of them, and Ishmael becomes an archer marrying an Egyptian like his mother.

  • vv. 22–32 - given the disastrous initial impression that Abraham made before Abimelech, by God’s grace, Abraham lived faithfully over a period of time and gained a godly reputation before Abimelech. Abimelech sees in Abraham what men would later see in Joseph, “God is with thee in all that thou doest” (v. 22). So the king wishes to form an alliance, which Abraham, knowing Abimelech’s character, is willing to do. However, he tells Abimelech that his servants had hijacked a well that belonged to Abraham. Wells were highly prized and formed a lucrative business as those passing would seek access to the water. Abraham asserts his ownership of the well and makes a covenant with the king to administer a greater sense of peace between them and their people. 

  • vv. 33–34 - Abraham plants a grove of trees in order to worship the God of Eternity Beersheba. 


  1. We must learn that living by faith is refusing to assess God’s promises by what we can see. God fulfilled all His promises concerning Isaac, despite every appearance of impossibility. Twice in vv. 1–2 we read of what God had spoken. Later we see God twice assuring that Ishmael would become a nation (vv. 13, 18). He had promised this in Gen. 17:20. Bottom line, what God has promised you may seem dim, but walk by faith, not by sight. 

  2. We need a lot of wisdom when dealing with rebellious older children. I would not take Abraham’s removal of Ishmael as policy, but it does reveal that the honor of God is higher than family. Pray you never are in this position.

  3. Just because someone has given bad advice in the past, doesn’t mean you should ignore them in the future. Sarah speaks as God’s mouthpiece, even though in the past she had judged things horribly wrong. 

  4. Once again we see Abraham exemplifying elder qualities. We saw him in his hospitality. Now we see him having, “a good report of them which are without.” Paul tells the Colossians to “Walk in wisdom toward them that are without.” Brother, if the world knows as a cranky Christian, it is probably because you are a cranky Christian. Repent and make it hard for the world to despise your God and your faith in Christ. 

  5. The mature Christian comes to realize that it is what happens in eternity that counts. This is no doubt part of what Abraham had in mind when he learned to refer to God as “the everlasting God” i.e. the God of eternity. You must live the same way. 

  6. The gospel of grace must be defended. Paul said he was “set for the defense of the gospel.” Ishmael believed he had a right, by flesh, to the divine benefits and blessings. Our response to this works righteousness religion is summarized in Galatians 5:1, “Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage.”

  7. This chapter foreshadows much relating to Christ. The fulfillment of God’s promise, the timing of the birth according to God’s Word, the miracle of the birth, the laughter that the birth brings. Sarah is like Mary, rejoicing in God her Savior. Children, you will never experience this kind of laughter until you know your sins are forgiven. Jesus taught us to rejoice not in success, but because our names are written in heaven. Is your name written in heaven? If not, why not? Talk to your parents about it today.

“If He is God, He must be true to His truth, and He will be, so, when I read a promise in His Word, I read something which is as certain as a fact already accomplished, since, if it were not to come to pass, God’s glory would suffer an eclipse, and His veracity would be impugned, and that can never be.” — Charles Spurgeon

Armen Thomassian