Genesis 17:25

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

Surrounding context

17:24 Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin.

17:25 And Ishmael his son was thirteen years old when he was circumcised in the flesh of his foreskin.

17:26 That very same day Abraham was circumcised, and his son Ishmael;