The Pastor's Class

The Promised Son

Genesis 21

Today we move from chapter 17 to chapter 21 and in so doing we skip over some very important material. In Chapter 18 the Lord again appears to Abraham in the form of three angel visitors. These angels reaffirm that Sarah will have a Son. Sarah overhears the conversation and laughs at the idea.

Before the Angels leave they tell Abraham what God has planned for Sodom and Gomorrah. (Remember Lot, Abraham's nephew had settled in Sodom.) Upon realizing that God planned to destroy Sodom and Gomorrah because of the wickedness in that city Abraham began to negotiate with God. Finally God agreed if there were as few as 10 righteous people in Sodom he would not destroy it.

In Chapter 19 two angels arrive at Sodom and upon Lot's insistence stay at his home. The Men of Sodom saw that Lot had two house guests demanded that they come out so that they could engage in sex with them. Lot tried to appease the angry mob by offering his two virgin daughters. Rejecting the offer the men of the city began to charge the door, but before they could gain entrance the Angels struck them with blindness.

With help from the Angels Lot and his family were able to escape however, Lot's wife disobeyed the order not to look back and she was destroyed. (turned to a pillar of salt).

The last part of chapter 19 records the sin of Lot's two daughters. Concerned that there was no one left to carry on the family name they devised a scheme to get their father drunk and commit the sin of insect with him. Both girls became pregnant by their father and each gave birth to a son. On son was named Moab and became the father of the Moabites. The other son was named Ben-Ammi and he became the father of the Ammonites.

In Chapter 20 we have another account where Abraham passes his wife Sarah off as his sister. Again we see the hand of God moving to protect Sarah from harm and to preserve her for His divine plan.

Genesis 21: 1-7

21 Now the LORD was gracious to Sarah as he had said, and the LORD did for Sarah what he had promised. 2 Sarah became pregnant and bore a son to Abraham in his old age, at the very time God had promised him. 3 Abraham gave the name Isaac to the son Sarah bore him. 4 When his son Isaac was eight days old, Abraham circumcised him, as God commanded him. 5 Abraham was a hundred years old when his son Isaac was born to him.

6 Sarah said, “God has brought me laughter, and everyone who hears about this will laugh with me.” 7 And she added, “Who would have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age.”

The New International Version, (Grand Rapids, MI: Zondervan Publishing House) 1984.

At the beginning of chapter 21 we see the fulfillment of God's promise. It has been now 25 years since the Lord first revealed his plan to Abraham. When God first spoke to Abraham he was 75 and Sarah was 65 it seemed pretty unlikely then that God could keep his promise. As time progressed, Abraham and Sarah concluded that the Lord needed some help so Ishmael was born. God later reaffirms his promise through the voice of visiting angels and Sarah laughs with disbelief. However, Chapter 21 opens with these words; "The Lord was gracious to Sarah as he had said, and the Lord did for Sarah what he had promised."

1. Chapter 21 begins with a testimony to God's faithfulness. What promise(s) has God fulfilled in your life?

As I stated in the sermon last week, "we determine character by what someone has already done and not by what he promises to do. However, once character has been established it is that very character that validates the promise.

The person who has little or no hope of God keeping his promises is the person who has little or no knowledge of his character.

If you ever doubt a promise of God take a moment and list all the promises that God has kept. It will give you confidence to wait upon those promises yet to be fulfilled.

2. Why did Abraham choose the eighth day of life to circumcise Isaac?

In Genesis 17:12, God specifically directed Abraham to circumcise newborn males on the eighth day. Why the eighth day? In 1935, professor H. Dam proposed the name “vitamin K” for the factor in foods that helped prevent hemorrhaging in baby chicks. We now know vitamin K is responsible for the production (by the liver) of the element known as prothrombin. If vitamin K is deficient, there will be a prothrombin deficiency and hemorrhaging may occur. Oddly, it is only on the fifth through the seventh days of the newborn male’s life that vitamin K (produced by bacteria in the intestinal tract) is present in adequate quantities. Vitamin K, coupled with prothrombin, causes blood coagulation, which is important in any surgical procedure. Holt and McIntosh, in their classic work, Holt Pediatrics, observed that a newborn infant has “peculiar susceptibility to bleeding between the second and fifth days of life.... Hemorrhages at this time, though often inconsequential, are sometimes extensive; they may produce serious damage to internal organs, especially to the brain, and cause death from shock and exsanguination” (1953, pp. 125-126). Obviously, then, if vitamin K is not produced in sufficient quantities until days five through seven, it would be wise to postpone any surgery until some time after that. But why did God specify day eight?

On the eighth day, the amount of prothrombin present actually is elevated above one-hundred percent of normal—and is the only day in the male’s life in which this will be the case under normal conditions. If surgery is to be performed, day eight is the perfect day to do it. Vitamin K and prothrombin levels are at their peak. The chart below, patterned after one published by S.I. McMillen, M.D., in his book, None of These Diseases, portrays this in graphic form.

Dr. McMillen observed:

We should commend the many hundreds of workers who labored at great expense over a number of years to discover that the safest day to perform circumcision is the eighth. Yet, as we congratulate medical science for this recent finding, we can almost hear the leaves of the Bible rustling. They would like to remind us that four thousand years ago, when God initiated circumcision with Abraham....

Abraham did not pick the eighth day after many centuries of trial-and-error experiments. Neither he nor any of his company from the ancient city of Ur in the Chaldees ever had been circumcised. It was a day picked by the Creator of vitamin K (1984, p. 93).

Moses’ information, as recorded in Genesis 17:12, not only was scientifically accurate, but was light-years ahead of its time. How did Moses have access to such information? The answer, of course, is provided by the apostle Paul in 2 Timothy 3:16—“Every scripture is inspired of God.”


Holt, L.E. and R. McIntosh (1953), Holt Pediatrics (New York: Appleton-Century-Crofts), twelfth edition.

McMillen, S.I. (1984), None of These Diseases (Old Tappan, NJ: Revell).

3. Verse 6 states that "Sarah laughed." Before we believed that Sarah and Abraham laughed out of disbelief. Now what does Sarah's laughter mean?

We can laugh out of disbelief and we can also laugh from delight. Obviously, Sarah is laughing here from delight.

When something good happens to us we sometimes say; "pinch me I must be dreaming." This must have been the attitude of Sarah. She laughed with delight and disbelief even though she knew it was real.

Genesis 21: 8 - 13

Hagar and Ishmael Sent Away

8 The child grew and was weaned, and on the day Isaac was weaned Abraham held a great feast. 9 But Sarah saw that the son whom Hagar the Egyptian had borne to Abraham was mocking, 10 and she said to Abraham, “Get rid of that slave woman and her son, for that slave woman’s son will never share in the inheritance with my son Isaac.”

11 The matter distressed Abraham greatly because it concerned his son. 12 But God said to him, “Do not be so distressed about the boy and your maidservant. Listen to whatever Sarah tells you, because it is through Isaac that your offspring will be reckoned. 13 I will make the son of the maidservant into a nation also, because he is your offspring.”

The New International Version, (Grand Rapids, MI: Zondervan Publishing House) 1984.

4. How old was Isaac when he was weaned?

It was the custom to wean a child somewhere between 2 - 3 years of age. This would be the age when a child could safely eat the same food adults ate so no special preparation was necessary. Also nursing served as a natural means of birth control.

5. According to the above passage what type of relationship did Sarah have with Ishmael? What type of relationship did Abraham have with Ishmael?

Ishmael continues to cause strife in the relationship. Once Isaac is born Sarah is ready once again to get rid of Hagar and Ishmael. Sarah commands that Abraham get rid of that slave woman and her son for he will never share in the inheritance with my son.

By this time Ishmael would be around 15 -16 years old. Abraham obviously had built a very close bond with his son. The bible says that this matter distressed him because it concerned his son.

Abraham was naturally drawn to his son Ishmael, however, since he was no blood kin to Sarah she found it easy to find fault with him.

This same strife and tension today can be seen in blended families. Parenting under the best of circumstances can be difficult. Parenting in a family where you are not the biological parent of some or all of the children can be next to impossible.

6. Why do you suppose God took Sarah's side in this conflict?

The above scripture affords us with a couple of oddities. First it would be unusual in that culture for a wife to speak in such a bold manner to her husband especially when it concerned his son. Maybe this speaks of the strength of the relationship.

Secondly, it would seem strange that God would side with Sarah. We generally think of God as being on the side of the outcast or downtrodden. However, here God agrees that this separation needs to take place.

We know from this chapter that Abraham loved his son Ishmael. We know from chapter 17 that Abraham would have been happy if Ishmael could have lived under God's covenant blessing.

God needed to make it perfectly clear to Abraham that the covenant promise would be through the lineage of Isaac and him alone.

This test of obedience would prepare Abraham for the ultimate test of obedience that would follow.

Genesis 21: 14 - 19

14 Early the next morning Abraham took some food and a skin of water and gave them to Hagar. He set them on her shoulders and then sent her off with the boy. She went on her way and wandered in the desert of Beersheba.

15 When the water in the skin was gone, she put the boy under one of the bushes. 16 Then she went off and sat down nearby, about a bowshot away, for she thought, “I cannot watch the boy die.” And as she sat there nearby, she began to sob.

17 God heard the boy crying, and the angel of God called to Hagar from heaven and said to her, “What is the matter, Hagar? Do not be afraid; God has heard the boy crying as he lies there. 18 Lift the boy up and take him by the hand, for I will make him into a great nation.”

19 Then God opened her eyes and she saw a well of water. So she went and filled the skin with water and gave the boy a drink.

The New International Version, (Grand Rapids, MI: Zondervan Publishing House) 1984.

7. What better way might Abraham have handled this situation?

The way Abraham treated Hagar and Ishmael seemed rather harsh. However, there are several things to consider. First, it was Sarah that made the decision not Abraham. Secondly, even though the text calls Ishmael a boy he is at least 15 and possibly 17 years old. He was not exactly helpless. Thirdly, Abraham was doing this with God's permission. Whereas it might seem as if Abraham were casting Hagar and his Son into the desert. Actually, he was releasing them into the care of the Lord.

Genesis 21: 20

20 God was with the boy as he grew up. He lived in the desert and became an archer. 21 While he was living in the Desert of Paran, his mother got a wife for him from Egypt.

The New International Version, (Grand Rapids, MI: Zondervan Publishing House) 1984.

8. If your mother could have chosen your mate who would she have chosen?

Normally it would be the father who would find a wife for the son. However, in this case the duty fell to Hagar. Since she was Egyptian she looked there for a wife for Ishmael.

Covenant between Abimelech and Abraham

The remainder of this chapter deals with a covenant between Abraham and a Philistine King named Abimelech.

Genesis 21: 22 - 24

22 At that time Abimelech and Phicol the commander of his forces said to Abraham, “God is with you in everything you do. 23 Now swear to me here before God that you will not deal falsely with me or my children or my descendants. Show to me and the country where you are living as an alien the same kindness I have shown to you.”

24 Abraham said, “I swear it.”

The New International Version, (Grand Rapids, MI: Zondervan Publishing House) 1984.

9. Why was Abimelech fearful of Abraham?

Abimelech had observed that God was with Abraham in everything that he did. Even though Abimelech was a pagan king who worshipped a pagan god he realized that The God of Abraham was mighty and strong.

10. Abimelech's request was the he be shown the same kindness that he had previously shown to Abraham. What kindness was that?

As stated earlier, Abraham had once again tried to pass Sarah off as his sister. This time to Abimelech. After the destruction of Sodom and Gomorrah Abraham went to Gerar. Abimelech, thinking Sarah was Abraham's sister took her into his harem. This was not an uncommon tradition in that day. This was one means of making an alliance between clans or families. Remember, by this time Sarah was well advanced in years and if she were indeed an unmarried sister this would have been a very charitable thing to do.

God intervenes and shows Abimelech the error of his ways and Abimelech offers Abraham livestock and silver as vindication.

Genesis 21: 25 - 34

25 Then Abraham complained to Abimelech about a well of water that Abimelech’s servants had seized. 26 But Abimelech said, “I don’t know who has done this. You did not tell me, and I heard about it only today.”

27 So Abraham brought sheep and cattle and gave them to Abimelech, and the two men made a treaty. 28 Abraham set apart seven ewe lambs from the flock, 29 and Abimelech asked Abraham, “What is the meaning of these seven ewe lambs you have set apart by themselves?”

30 He replied, “Accept these seven lambs from my hand as a witness that I dug this well.”

31 So that place was called Beersheba, because the two men swore an oath there.

32 After the treaty had been made at Beersheba, Abimelech and Phicol the commander of his forces returned to the land of the Philistines. 33 Abraham planted a tamarisk tree in Beersheba, and there he called upon the name of the LORD, the Eternal God. 34 And Abraham stayed in the land of the Philistines for a long time.

The New International Version, (Grand Rapids, MI: Zondervan Publishing House) 1984.

11. Why would two great men like Abraham and Abimelech quarrel over such a small thing as a well?

In that arid and dry climate water was vital to survival. Herdsmen would often quarrel over wells and water rights. You can imagine how much water it would take to water a thousand or more head of livestock.

Even though Abraham was living as an alien he was able to claim ownership of this particular well because he dug it.

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