When God Brings Life Out of the Impossible -Genesis 21

Hyunjin Lee
Dec 11, 2025
4 min read

Genesis 21 is a powerful testimony of God’s faithfulness, sovereignty, and tender care. In this chapter, Isaac—the child of promise—is finally born. Yet we also see deep family conflict, painful separation, and God’s mercy extended even to those outside the covenant line.

This chapter teaches us that God keeps His promises, He works beyond human ability, and He watches over those who feel forgotten.

1. God Works Behind the Scenes to Fulfill His Promise (Genesis 21:1)

“The Lord did for Sarah what He had promised.”

This verse highlights God’s direct and supernatural action. Sarah conceived because God Himself intervened. Matters of birth and death, and all of life, fall under God’s sovereignty (Isaiah 44:2). At ninety years old, Sarah’s body was barren—and yet she received the ability to conceive because she believed in God’s power (Hebrews 11:11).

2. God Fulfills His Word at His Appointed Time (Genesis 21:2)

Isaac was born “at the very time God had promised.” This refers to the covenant timeline God set in Genesis 17:21.

Why did God wait more than 13 years after the initial promise?

(1) To show His miracle clearly

God waited until Abraham was one hundred years old and “as good as dead” physically (Romans 4:19). This delay emphasized that Isaac’s birth was completely dependent on God, not human strength (Hebrews 11:11–12).

(2) To allow Ishmael to grow to independence

Part of the covenant storyline required Ishmael to reach an age where he could live on his own (Genesis 21:13, 21).

God’s timing is never random—it is wise, purposeful, and perfect.

3. The Birth of the Promised Son (Genesis 21:3–7)

After decades of longing, waiting, and disappointment, the promised seed finally arrives. Isaac is one of the most anticipated figures in the Old Testament because he is a foreshadow of Christ, the true “first fruits” of resurrection (1 Corinthians 15:20,23). His life ultimately points forward to the sacrifice on Mount Moriah (Genesis 22), which prefigures the sacrifice of Jesus.

4. Sarah’s Demand to Expel Hagar and Ishmael (Genesis 21:10)

“Cast out this slave woman and her son.”

Sarah emphasizes Hagar’s status as a servant to make the legal point that a slave’s son could not inherit with the true heir.

The Hebrew word garash (“cast out”) can also mean to dismiss legally, similar to divorce, implying a permanent legal separation from Abraham’s household.

According to ancient customs (confirmed in the Nuzi Tablets), Sarah’s demand was permissible. Yet emotionally, it feels harsh and contradictory, especially because she herself had given Hagar to Abraham years earlier (Genesis 16:2).

5. Abraham’s Deep Distress (Genesis 21:11)

Abraham is torn for two reasons:

His fatherly love for Ishmael, whom he once hoped would be his heir (Genesis 17:18).
Cultural custom—a servant who bore a child for her master was not to be expelled lightly. This made the situation emotionally and socially difficult.

Abraham is caught between compassion and obedience.

6. God Reassures Abraham Concerning Ishmael (Genesis 21:13)

God repeats His promise:“I will make the son of the slave woman into a nation also.”

This affirms God’s compassion and His earlier covenant blessing toward Ishmael (Genesis 17:20).God’s repeated words show His deep care for Abraham’s emotional pain.

Ultimately, Ishmael fathers twelve princes, fulfilling the promise (Genesis 25:12–16).

7. Abraham Sends Them Away in Obedience (Genesis 21:14)

“Early the next morning…”

Abraham acts immediately, in contrast to his earlier emotional turmoil. His obedience is clear and wholehearted.

He provides bread and water—the basic necessities for traveling. Scripture does not mention it, but considering his wealth and affection (Genesis 13:2; 20:14–16), it is likely he gave additional resources.

Hagar wanders in the wilderness of Beersheba, probably attempting to return to Egypt but losing her way after twenty years away from her homeland.

8. Hagar’s Despair in the Wilderness (Genesis 21:15–16)

When the water runs out, death seems inevitable—especially for Ishmael, who had not grown up accustomed to harsh desert conditions.

Hagar sits at a distance, unable to watch her son die, and cries out in deep anguish.

9. God Hears the Cry of the Boy (Genesis 21:17)

God appears here as Elohim, the God of power and creation, rather than Yahweh, the covenant name. This signals that although Hagar and Ishmael are outside the covenant line, they are still under God’s universal care.

The angel of God speaks tenderly to her:

“Do not be afraid.”

This is the same divine comfort spoken to Abraham (Genesis 15:1), Isaac (26:24), Daniel (Daniel 10:12), and John (Revelation 1:17).God’s comfort is timeless—still offered to all who look to Him in their distress.

10. God’s Promise Over Ishmael (Genesis 21:18)

“Lift up the boy… I will make him into a great nation.”

The Hebrew hazak (“lift up”) means strengthen, hold firmly, encourage. God tells Hagar to take courage and actively support Ishmael until he grows.

This promise shows that God can take an insignificant and dying boy in the wilderness and turn him into the forefather of a vast people. This is how God works—lifting the lowly and making the weak into something great (1 Corinthians 1:26–29).