Genesis 21:2-4

Young's Literal Translation

² and Sarah conceiveth, and beareth a son to Abraham, to his old age, at the appointed time that God hath spoken of with him;

³ and Abraham calleth the name of his son who is born to him, whom Sarah hath born to him -- Isaac;

⁴ and Abraham circumciseth Isaac his son, [being] a son of eight days, as God hath commanded him.