Genesis 17:23 WEB

²¹  But my covenant I establish with Isaac, whom Sarah will bear to you at this set time in the next year.'

²²  When he finished talking with him, God went up from Abraham.

²³  Abraham took Ishmael his son, all who were born in his house, and all who were bought with his money; every male among the men of Abraham's house, and circumcised the flesh of their foreskin in the same day, as God had said to him.

²⁴  Abraham was ninety-nine years old, when he was circumcised in the flesh of his foreskin.

²⁵  Ishmael, his son, was thirteen years old when he was circumcised in the flesh of his foreskin.