Genesis 21:1-8

Then the LORD took note of Sarah as He had said, and the LORD did for Sarah as He had promised. So Sarah conceived and bore a son to Abraham in his old age, at the appointed time of which God had spoken to him. 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. Sarah said, “God has made laughter for me; everyone who hears will laugh with me.” And she said, “Who would have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age.” The child grew and was weaned, and Abraham made a great feast on the day that Isaac was weaned.