David Guzik :: Study Guide for Genesis 21

The Birth of Isaac

A. The birth of Isaac.

1. (Genesis 21:1) 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. (Genesis 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 something 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 the Messiah to come, Jesus Christ.

• Both were specially promised sons.
• Both conceptions were miraculous.
• Both were born after a period of delay.
• Both mothers were given assurance by truth of 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 accompanied by great joy (Genesis 21:6; Luke 1:46-47; 2:10-11).

B. The conflict between Ishmael and Isaac.

1. (Genesis 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 approximately 13 years apart in age. Abraham found it hard to agree with Sarah’s complaint, when he did not want to reject his son through Hagar, Ishmael.

i. Notice the conflict came from Ishmael unto Isaac. Ishmael was the one scoffing at Isaac. In Galatians 4:22-29, the Apostle Paul used this conflict as an illustration of the conflict between those born of the promise and those 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, yet in reliance upon human strength and wisdom (the flesh), do in fact persecute those who follow God in faith through the promise.

2. (Genesis 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 considered the son of Hagar something 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 in a 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. (Genesis 21:15-18) 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.”

a. The water in the skin was used up: As Hagar and Ishmael traveled away from Abraham, their supplies eventually ran out. Their water was used up and Hagar left Ishmael under the shade of one of the shrubs, expecting their soon death in the wilderness.

i. “Behold the compassion of a mother for her child expiring with thirst, and remember that such a compassion ought all Christians to feel towards souls that are perishing for lack of Christ, perishing eternally, perishing without hope of salvation.” (Spurgeon)

b. God heard the voice of the lad: As Hagar lifted her voice and wept, God answered. Curiously, God answered in response to the voice of the lad instead of specifically to Hagar’s weeping. In some way, Ishmael cried out for mercy and help.

c. Fear not, for God has heard the voice of the lad where he is: Despite the desperate problem in the wilderness, God’s promise gave Hagar and Ishmael reason to fear not. God showed special favor to Ishmael because he was a descendant of Abraham.

d. I will make him a great nation: Though Ishmael was not the son to receive the covenant promise, God was not against him. The descendants of Ishmael became a great nation, the Arabic people.

4. (Genesis 21:19-21) God’s provision for Hagar and Ishmael.

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. Then God opened her eyes, and she saw a well of water: Whether the miracle was in the creation of a water source or the revealing of an existing water source, God provided for Hagar and Ishmael.

i. Spurgeon explained the likeness between Hagar and the one who needs God. “As in Hagar’s case, the supply of their necessities is close at hand: the well is near. Secondly, it often happens that that supply is as much there as if it had been provided for them and for them only, as this well seemed to have been. And, thirdly, no great exertion is needed to procure from the supply already made by God all that we want. She filled her bottle with water — a joyful task to her; and she gave the lad drink.”

b. So God was with the lad: The idea is emphasized that God was not against Ishmael and his descendants. God was with Ishmael, and had a promise for his future.

C. Abraham makes a covenant with a Philistine king.

1. (Genesis 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. This ruler and Phichol, the commander of his army, met with Abraham.

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. Abraham had the greatest of all blessings: the presence of God in his life.

i. “I think that the greatest blessing God ever gives to a man is his own presence. If I had my choice of all the blessings of this life, I certainly should not ask for wealth, for that can bring no ease; and I certainly should not ask for popularity, for there is no rest to the man upon whose words men constantly wait, and it is a hard task one has to perform in such a case as that; but I should choose, as my highest honor, to have God always with me.” (Spurgeon)

c. Swear to me by God that you will not deal falsely with me: Because God had so blessed Abraham, he was a man of great wealth, influence, and power. Abimelech knew that it was important to have Abraham in favor towards him and his descendants. Abraham agreed, saying “I will swear.”

2. (Genesis 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.

a. Then Abraham rebuked Abimelech because of a well: Because Canaan had no significant rivers and a great reliance upon rain, a well was an important and strategic property. Apparently, Abraham was in possession of a well of water that Abimelech’s servants had seized. The man of faith did not simply accept this wrong; he rebuked Abimelech because of a well.

b. Abraham took sheep and oxen and gave them to Abimelech, and the two of them made a covenant: The sheep and oxen were probably used as sacrifices to make or cut the covenant, as in Genesis 15:7-21.

c. You will take these seven ewe lambs from my hand: The seven ewe lambs were special gifts from Abraham to Abimelech to show favor and offer some compensation for his loss of access to the well. Abraham understood his own property rights, but was not greedy or miserly. The acceptance of the seven lambs was Abimelech’s recognition that Abraham had dug this well and it belonged to him.

d. Therefore he called that place Beersheba: This was a descriptive name. Beersheba means watering place, well of underground water. Some understand the Biblical name Beersheba as well of seven or well of the oath. Beersheba would become a notable place in Israel’s continuing history, and continues today as an important city in modern Israel (Beer-Sheva).

• Abraham’s son Isaac dug this well again, and he built an altar in Beersheba (Genesis 26:23-33).
• Abraham’s grandson Jacob stopped in Beersheba as he left the promised land (Genesis 28:10-15, 46:1-7).
• When Israel took possession of the promised land, Beersheba became the territory of the tribe of Simeon and Judah (Joshua 15:28, 19:2).
• Samuel’s sons were judges in Beersheba (I Samuel 8:2).
• King Saul fortified Beersheba in his battles against the Amalekites (I Samuel 14:48, 15:2-9).
• The prophet Elijah found refuge at Beersheba when Jezebel ordered him killed (I Kings 19:3).
• The prophet Amos mentioned Beersheba in regard to idolatry (Amos 5:5 and 8:14).

i. The phrase from Dan to Beersheba would later become a proverbial phrase describing the entire land of Israel, from north (Dan) to south (Beersheba). This is seen in passages such as Judges 20:1, 1 Samuel 3:20, 2 Samuel 3:10, 1 Kings 4:25, and many others.

3. (Genesis 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. Abraham planted a tamarisk tree in Beersheba: After the successful treaty, Abraham did something that looked forward to coming decades and generations. A tamarisk tree takes a long time to grow, but Abraham knew God had promised the land to him and his descendants forever.

b. 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 did not drive him away from God, but he allowed it to push him closer to the LORD.

©2018 David Guzik - No distribution beyond personal use without permission

Updated: August 2022