Genesis 21:2-5

WEB(i) 2 Sarah conceived, and bore Abraham a son in his old age, at the set time of which God had spoken to him. 3 Abraham called his son who was born to him, whom Sarah bore to him, Isaac. 4 Abraham circumcised his son, Isaac, when he was eight days old, as God had commanded him. 5 Abraham was one hundred years old when his son, Isaac, was born to him.