The Promise Fulfilled: Genesis Chapter 21 Bible Study

Introduction

Welcome back to The Daily Manna!

In Genesis 21, we witness one of the most joyful moments in Scripture, the long-awaited fulfillment of God’s promise to Abraham and Sarah. After years of waiting, laughter fills their home as Isaac is born. Yet, alongside joy comes testing as tension rises between Sarah and Hagar, and Abraham must once again trust God’s direction. This chapter reminds us that God’s promises never fail, though His timing may stretch our faith.

Before reading on, take a moment to read Genesis 21 in full. This study is meant to guide reflection, not replace the Word of God itself.

Summary of Genesis 21

Genesis 21:1–7 – The Birth of Isaac

The Lord keeps His promise, and Sarah conceives and gives birth to Isaac in her old age. Abraham names him Isaac, meaning “laughter,” as both he and Sarah rejoice in God’s faithfulness.

Genesis 21:8–13 – Hagar and Ishmael Sent Away

During a feast celebrating Isaac’s weaning, Sarah notices Ishmael mocking Isaac. She insists that Abraham send Hagar and Ishmael away. Though troubled, Abraham obeys after God reassures him that His covenant will continue through Isaac — but that He will also bless Ishmael and make him a great nation.

Genesis 21:14–21 – God’s Care for Hagar and Ishmael

Hagar and Ishmael wander in the desert of Beersheba, running out of water. In her despair, God hears Ishmael’s cry and provides a well, promising to make him into a great nation. Even outside the covenant line, God’s compassion and provision shine through.

Genesis 21:22–34 – The Treaty at Beersheba

Abimelek and Abraham make a peace treaty at Beersheba. Abraham plants a tamarisk tree and calls on the name of the Lord, showing his trust in God’s lasting promises and provision in the land.

Key Themes and Meaning

God’s Promises Never Fail

Genesis 21:1–2 NIV

“Now the Lord was gracious to Sarah as He had said, and the Lord did for Sarah what He had promised.”

What we need to learn from this chapter is that what God promises, He performs. As in he provides for. Though Abraham and Sarah waited many years, God’s timing was perfect. His word is certain even when circumstances make it seem impossible. 

God’s Timing Brings Joy After Waiting

Genesis 21:6 NIV

“Sarah said, ‘God has brought me laughter, and everyone who hears about this will laugh with me.’”

God often delays fulfillment to deepen our faith. When His promise finally comes, the joy outweighs the waiting. Sarah’s laughter turns from disbelief to delight — a reminder that joy comes when we trust His timing.

     I would like to point out here that Isaac was a miracle child. Which is a picture of us as Christians. God had provided to Abraham and Sarah in a miraculous way that without help their bodies could not have produced on their own. 

       Only through acceptance of Christ can we be born of spirit. The story of Isaac is kind of a foreshadowing of that. An example of this is in John 1:12-13: 

 “ 12. Yet to all who did receive him, to those who believed in his name, he gave the right to become children of God - 13. children born not of natural descent, nor of human decision or a husband's will, but born of God”

From here we see the child grows and was weaned and on the day he was weaned Abraham holds a feast. But Sarah saw Hagar's son Ishmael was mocking so she told Abraham to get rid of the slave woman and her son for that woman's son will never share in the inheritance of her son Isaac. This sounds really harsh at surface level. After all Ishmael's probably a teenager. However let's look a little deeper at this. 

Galatians 4:24-25, 28-30 NIV

[24] These things are being taken figuratively: The women represent two covenants. One covenant is from Mount Sinai and bears children who are to be slaves: This is Hagar. [25] Now Hagar stands for Mount Sinai in Arabia and corresponds to the present city of Jerusalem, because she is in slavery with her children. 

[28] Now you, brothers and sisters, like Isaac, are children of promise. [29] At that time the son born according to the flesh persecuted the son born by the power of the Spirit. It is the same now. [30] But what does Scripture say? “Get rid of the slave woman and her son, for the slave woman’s son will never share in the inheritance with the free woman’s son.” 

The two brothers Isaac and Ishmael represent Spirit and flesh. Now as we said above Isaac represents spirit because he's born of God and will be the lineage that God chose. Isaac is the picture of those born only of the flesh. 

I would like to point out here that nobody can be saved by the flesh only by faith in Jesus which is the rebirth of the Spirit. We see this when Jesus talks to Nicodemus in the book of John 3:1-21

God’s Mercy Extends Beyond the Covenant

When Sarah told Abraham to get rid of the slave woman and her son, he was greatly distressed concerning his son. But God told him not to be distressed to listen to what Sarah tells him, because it is through Isaac that his offspring will be reckoned. However because of the goodness of God he says “I will make the son of the slave into a nation also because he is your offspring” 

Which means even though Ishmael wasn't the chosen lineage, He was still Abraham's son, therefore he was blessed. 

From here we see Abraham taking some food and a skin of water and giving them to Hagar and he sent them off. They started to wonder in the desert of Beersheba. From there the water in the skin was gone so she put her son under one of the bushes and she went off and sat down about 100 yards away and she started to cry saying that she couldn't watch her son die. 

Genesis 21:17–18 NIV

“God heard the boy crying, and the angel of God called to Hagar from heaven and said to her, ‘Do not be afraid; God has heard the boy crying as he lies there.’”

Even though Ishmael was not the child of promise, God still cared for him. His mercy reaches beyond boundaries, revealing His heart for all people. 

Then God opened Hagar's eyes and she saw a well of water. Here we see God providing for them. We also see that as the boy grew up God was with him. Ishmael lives in the desert and becomes an archer. 

Faith Requires Letting Go

Genesis 21:12 NIV

“But God said to him, ‘Do not be distressed about the boy and your slave woman; listen to whatever Sarah tells you, because it is through Isaac that your offspring will be reckoned.’"

How hard that must have been for Abraham, watching his firstborn son leave. Obedience sometimes means releasing what we love or understand. Abraham’s faith was tested again, yet he trusted that God’s plan was greater than his pain. 

Reflections for Today

1. Have I grown impatient waiting for God’s promises in my life?

2. How can I keep trusting God’s timing when the wait feels long?

3. What joy or laughter has God brought out of my seasons of waiting?

4. Do I trust God’s mercy to reach even those outside my comfort zone?

5. Is there something God is asking me to release so I can move forward in faith?

Conclusion

Genesis 21 reminds us that God’s promises never fail. His timing may not match ours, but His faithfulness always brings joy. Through laughter, loss, and letting go, Abraham and Sarah’s story teaches us that God’s plan is worth the wait.

When we face long seasons of uncertainty, may we remember that every promise of God finds its “Yes” in Him, and that He always keeps His word.

Prayer

Heavenly Father,

Thank You for being a God who keeps Your promises. Help me to trust Your timing, even when the wait feels long. Give me faith to let go of what no longer fits Your plan and to rejoice when Your promises are fulfilled. Thank You for Your mercy that reaches beyond what I can see.

In Jesus’ name, Amen.