Genesis 21:4-8

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

Now Abraham was a 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 given birth to a son in his old age.”

And the child grew and was weaned, and Abraham held a great feast on the day that Isaac was weaned. Sarah Turns against Hagar