Moses commanded you to circumcise your sons. But it wasn't really Moses who gave you this command. It was your ancestors, and even on the Sabbath you circumcise your sons
God said to Abraham, “Every son in each family must be circumcised to show that you have kept your agreement with me.” So when Isaac was eight days old, Abraham circumcised him. Later, Isaac circumcised his son Jacob, and Jacob circumcised his twelve sons.