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The Blue Letter Bible

David Guzik :: Study Guide for Genesis 21

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The Birth of Isaac

A. The birth of Isaac.

1. (1) God fulfills His promise to Abraham and Sarah.

And the Lord visited Sarah as He had said, and the Lord did for Sarah as He had spoken.

a. The Lord visited Sarah as He had said: It took a long time (25 years) for this promise to come to pass, but God was faithful to His promise. God’s promises never fail.

b. As He had spoken: The promise of a son was not fulfilled because Abraham was perfect in his obedience, but because God was faithful to His Word.

i. Some promises of God are conditional and depend on something we must do. Other promises of God are unconditional, and God will fulfill them not because of what we do, but because of who He is.

2. (Gen 21:2-7) The child is named Isaac.

For Sarah conceived and bore Abraham a son in his old age, at the set time of which God had spoken to him. And Abraham called the name of his son who was born to him; whom Sarah bore to him; Isaac. Then Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. Now Abraham was one hundred years old when his son Isaac was born to him. And Sarah said, “God has made me laugh, and all who hear will laugh with me.” She also said, “Who would have said to Abraham that Sarah would nurse children? For I have borne him a son in his old age.”

a. Abraham called the name of his son who was born to him; whom Sarah bore to him; Isaac: Originally, the name Isaac was meant as somewhat of a rebuke of the laughter of Abraham and Sarah (Genesis 17:17-19 and 18:12-15), but God turned a gentle rebuke into an occasion for joy.

b. Isaac: Isaac became a wonderful type or picture of Jesus.

· Both were specially promised sons.
· Both were born after a period of delay.
· Both mothers were assured by God’s omnipotence (Genesis 18:13-14; Luke 1:34, 37).
· Both were given names rich with meaning before they were born.
· Both births occurred at God’s appointed time (Genesis 21:2; Galatians 4:4).
· Both births were miraculous.
· Both births were accompanied by joy (Genesis 21:6; Luke 1:46-47; 2:10-11).

B. Conflict between Ishmael and Isaac.

1. (Gen 21:8-11) Sarah wants Abraham to cast out both Hagar and Ishmael.

So the child grew and was weaned. And Abraham made a great feast on the same day that Isaac was weaned. And Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, scoffing. Therefore she said to Abraham, “Cast out this bondwoman and her son; for the son of this bondwoman shall not be heir with my son, namely with Isaac.” And the matter was very displeasing in Abraham’s sight because of his son.

a. The child grew and was weaned: Some ancients say children were not weaned until 12 years of age and some say five years, but the most reliable research indicates an age of three. Isaac was young.

b. And Sarah saw the son of Hagar…scoffing: This conflict between the two sons was almost inevitable, even though they were some 13 years apart. Abraham found it hard to agree with Sarah’s complaint when he did not want to reject his son, Ishmael.

i. Notice the conflict came from Ishmael unto Isaac. Ishmael was the one scoffing at Isaac. Galatians 4:22-29 describes for us a spiritual application of this conflict between Isaac (the son born of the promise) and Ishmael (the son born of the flesh).

ii. In Galatians 4, the Jewish legalists who troubled the Galatians protested they were children of Abraham and thus blessed. Paul admitted they were children of Abraham, but they were like Ishmael, not Isaac! The legalists claimed Abraham as their father. Paul asked who was their mother, Hagar or Sarah? Ishmael was born of a slave, and born according to the flesh. Isaac was born of a freewoman, and born according to promise. Even so, the legalists promoted a relationship with God based in bondage and according to the flesh. The true gospel of grace offers liberty in Jesus Christ and is a promise received by faith.

iii. Even as Ishmael and his descendants have persecuted Isaac and his descendants, we should not be surprised that the modern-day people who follow God in the flesh persecute those who follow God in faith through the promise.

2. (Gen 21:12-14) Under God’s instruction, Abraham puts out Hagar and Ishmael.

But God said to Abraham, “Do not let it be displeasing in your sight because of the lad or because of your bondwoman. Whatever Sarah has said to you, listen to her voice; for in Isaac your seed shall be called. Yet I will also make a nation of the son of the bondwoman, because he is your seed.” So Abraham rose early in the morning, and took bread and a skin of water; and putting it on her shoulder, he gave it and the boy to Hagar, and sent her away. Then she departed and wandered in the Wilderness of Beersheba.

a. Whatever Sarah has said to you, listen to her voice: Perhaps Abraham did not want to give up Ishmael because he was sort of a backup plan. If something should happen to Isaac, there would always be Ishmael. God did not want Abraham to trust in a backup son or backup plan. God wanted Abraham to trust in Him.

i. Abraham might have been tempted to reject Sarah’s counsel just because it was Sarah who offered it. Instead he sought the Lord in the matter, did what Sarah suggested, and did so apparently without feeling he merely gave in to Sarah’s demands.

b. Sent her away: God’s solution was clear – get rid of the son of the flesh. There was to be no reconciliation with the flesh, no peaceful coexistence. The son of the flesh must simply be put away forever.

i. The solution is the same in our own battle between trusting in the flesh and trusting in the Holy Spirit: cast out this bondwoman and her son. Law and grace cannot live together as principles for our Christian life, and there is no question we belong to the free, not the bondwoman.

c. Then she departed and wandered in the Wilderness of Beersheba: It may have seemed ruthless of Abraham to do this, but it was exactly what God wanted, and exactly what needed to happen.

i. Flesh and blood do not make the strongest bond God wants us to honor. There are circumstances where we can do nothing other than put away family for the glory of God.

ii. God wants us to be ruthless with the flesh in the same manner: And those who are Christ’s have crucified the flesh with its passions and desires (Galatians 5:24).

d. Took bread and a skin of water: Abraham was a wealthy man and could certainly afford to give them more supplies, even giving them a donkey or several pack animals. Yet Abraham realized that without God’s help, no matter what he gave them, it would not be enough. But with God, things would turn out all right.

3. (Gen 21:15-21) God preserves Ishmael and Hagar in the desert.

And the water in the skin was used up, and she placed the boy under one of the shrubs. Then she went and sat down across from him at a distance of about a bowshot; for she said to herself, “Let me not see the death of the boy.” So she sat opposite him, and lifted her voice and wept. And God heard the voice of the lad. Then the angel of God called to Hagar out of heaven, and said to her, “What ails you, Hagar? Fear not, for God has heard the voice of the lad where he is. Arise, lift up the lad and hold him with your hand, for I will make him a great nation.” Then God opened her eyes, and she saw a well of water. And she went and filled the skin with water, and gave the lad a drink. So God was with the lad; and he grew and dwelt in the wilderness, and became an archer. He dwelt in the Wilderness of Paran; and his mother took a wife for him from the land of Egypt.

a. Fear not, for God has heard the voice of the lad where he is: As God protected and preserved them out in the desert; He answered them by hearing the voice of the lad. God showed special favor to Ishmael because he was a descendant of Abraham.

b. I will make him a great nation: The descendants of Ishmael became the Arabic people.

C. Abraham makes a covenant with a Philistine king.

1. (Gen 21:22-24) Abraham makes a no-hostility treaty with Abimelech.

And it came to pass at that time that Abimelech and Phichol, the commander of his army, spoke to Abraham, saying, “God is with you in all that you do. Now therefore, swear to me by God that you will not deal falsely with me, with my offspring, or with my posterity; but that according to the kindness that I have done to you, you will do to me and to the land in which you have dwelt.” And Abraham said, “I will swear.”

a. Abimelech…spoke to Abraham: This was probably not the same Abimelech of Genesis 20. Abimelech was the title of a ruler among the Canaanites, not a specific name.

b. God is with you in all that you do: Abimelech noticed this because of Abraham’s integrity and because of the blessing evident in his life.

2. (Gen 21:25-31) In return for the treaty, Abraham clears up a dispute about an important well.

Then Abraham rebuked Abimelech because of a well of water which Abimelech’s servants had seized. And Abimelech said, “I do not know who has done this thing; you did not tell me, nor had I heard of it until today.” So Abraham took sheep and oxen and gave them to Abimelech, and the two of them made a covenant. And Abraham set seven ewe lambs of the flock by themselves. Then Abimelech asked Abraham, “What is the meaning of these seven ewe lambs which you have set by themselves?” And he said, “You will take these seven ewe lambs from my hand, that they may be my witness that I have dug this well.” Therefore he called that place Beersheba, because the two of them swore an oath there.

3. (Gen 21:32-34) Abraham calls on the name of the Lord.

Thus they made a covenant at Beersheba. So Abimelech rose with Phichol, the commander of his army, and they returned to the land of the Philistines. Then Abraham planted a tamarisk tree in Beersheba, and there called on the name of the Lord, the Everlasting God. And Abraham stayed in the land of the Philistines many days.

a. Called on the name of the Lord, the Everlasting God: Even through this time of conflict in his family and among his neighbors, Abraham kept a real, live walk with God. Conflict can drive us away from God, but we should allow it to push us closer to Him.

©2013 David Guzik – No distribution beyond personal use without permission
[A previous revision of this page can be found here]

Study Guide for Revelation 1 ← Prior Book
Study Guide for Exodus 1 Next Book →
Study Guide for Genesis 20 ← Prior Chapter
Study Guide for Genesis 22 Next Chapter →
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