Genesis 21:5

3Abraham called his son who was born to him, whom Sarah bore to him, Isaac.

4Abraham circumcised his son, Isaac, when he was eight days old, as God had commanded him.

5Abraham was one hundred years old when his son, Isaac, was born to him.

6Sarah said, “God has made me laugh. Everyone who hears will laugh with me.”

7She said, “Who would have said to Abraham that Sarah would nurse children? For I have borne him a son in his old age.”