Genesis 21:1 - Meaning and Application

The long-awaited moment finally came. God’s promise about the coming offspring had a set time, and now it spoke true and did not fail. Few people in the Old Testament were born with such deep expectation as Isaac, not because he would become a great man in worldly terms, but because he would be a type of Christ, that promised seed whom God had long said would come and whom holy people had long awaited.

In this account of Isaac’s early days, we can see how God kept his promise in Isaac’s conception and birth (Genesis 21:1, 2). God’s works look clearest when we compare them with his word, and then we see how closely he does what he said he would do. Isaac was born just as the promise said. The Lord showed mercy to Sarah, as he had said. No word from God will fail, because he is faithful to his promise, and his faithfulness is the support of his people’s faith. Isaac was born at the exact time God had spoken of. God is always on time. His promised blessings may not come when we choose, but they will surely come when he chooses, and that is always the best time.

Isaac was also born because of the promise. Sarah received strength to conceive by faith (Hebrews 11:11). So God gave that strength through his promise. This was not the result of ordinary providence, but of God’s special promise. Human hope had reached the point of death, as it were. Abraham was old, Sarah was old, and both were as good as dead. Then God’s word took effect. True believers, by God’s promises, are enabled to do what is beyond human strength, because through those promises they share in the divine nature (2 Peter 1:4).

We also see Abraham obeying God’s command about Isaac. He gave him the name God had ordered, Genesis 21:3. God had chosen the name Isaac, which means laughter, as a reminder, and Abraham gave him that name, even though he might have chosen something grander. Human ideas should always yield to God’s wisdom and plain command. The name fit well. When Abraham first heard the promise, he laughed for joy (Genesis 17:17). It is good to remember the joy we felt when comfort first dawned on us, and to recall how gladly we embraced God’s promise. Sarah had laughed at first from doubt and weakness of faith. When God gives us blessings we had almost given up on, we should remember our sinful distrust with sorrow and shame. Isaac was later mocked by Ishmael (Genesis 21:9), and his name may have helped prepare him for that. God’s favored ones are often made into the world’s laughingstock. Yet the promise he inherited was meant to become the joy of all saints in every age, filling their mouths with laughter.

Abraham also circumcised Isaac on the eighth day (Genesis 21:4). Since the covenant was established with him, the sign of the covenant was given to him. Though it was a painful rite and Isaac was dearly loved, it still could not be left out or delayed beyond the eighth day. God had kept time in fulfilling the promise, so Abraham had to keep time in obeying the command.

Sarah was deeply affected by this mercy. First, it filled her with joy (Genesis 21:6). “God has made me laugh,” she said. He gave her both a reason to rejoice and a heart to rejoice. Mary, the mother of Jesus, spoke in the same way (Luke 1:46, 47). God gives his people blessings to stir up joy in his work and service, and whatever gives us true joy should be traced back to him, unless it is the empty laughter of a fool. When blessings have been long delayed, they are all the sweeter when they arrive. It also adds much to any blessing when others rejoice with us. “Everyone who hears about it will laugh with me,” Sarah said, because joy spreads easily. Others would rejoice in this display of God’s power and goodness, and be encouraged to trust him more fully (Psalm 119:74).

This mercy also filled Sarah with wonder (Genesis 21:7). What amazed her most was that she should nurse children, meaning that she not only bore a child but was still strong enough, at her age, to nurse him. Mothers, if they are able, should nurse their own children. Sarah was a woman of rank and was elderly. Nursing might have seemed harmful to herself, the child, or both. She surely had other servants or nurses available in her household. Yet she chose to do her duty in this matter. In doing so, she showed the godly conduct praised in women who do what is right (1 Peter 3:5, 6). See also Lamentations 4:3.

Sarah then expressed her amazement by saying, “Who would have said it?” The thing seemed so unlikely, almost impossible, that if anyone but God had said it, no one could have believed it. God’s blessings to his covenant people go beyond what they or others expect. Who could have imagined that God would do so much for people who deserved so little, and even for people who deserved so badly? See Ephesians 3:20 and 2 Samuel 7:18, 19. Who would have thought God would send his Son to die for us, his Spirit to make us holy, and his angels to care for us? Who would have said that such great sins would be forgiven, such weak service accepted, and such unworthy people brought into covenant and fellowship with the great and holy God?

We are then told briefly about Isaac’s early growth. “The child grew” (Genesis 21:8). This is mentioned, even though it is expected, to show that the children of the promise are growing children. See Luke 1:80 and Luke 2:40. Those who are born of God will keep growing in God’s life and grace (Colossians 2:19). Isaac grew until he no longer needed milk and was ready for solid food, and then he was weaned. See Hebrews 5:13, 14. At that point Abraham made a great feast for his friends and neighbors, giving thanks to God for his mercy. He did not make the feast on the day Isaac was born, because that would have upset Sarah too much. He did not make it on the day Isaac was circumcised, because that would have distracted from the holy ordinance. He made it when Isaac was weaned, because God’s blessing on children during nursing, and his care for them through the dangers of infancy, are clear signs of divine tenderness that should be praised. See Psalm 22:9, 10 and Hosea 11:1.