Genesis 21:2-5
Genesis 21: 2 to 5
2 For Sarah conceived, and bore Abraham a son in his old age, at the set time of which God had spoken to him.
3 And Abraham called the name of his son that was born to him, whom Sarah bore to him, Isaac.
4 And Abraham circumcised his son Isaac being eight days old, as God had commanded him.
5 And Abraham was an hundred years old, when his son Isaac was born to him.