Genesis 17:18

That Ishmael might live before thee! This plea suggests that ever since the birth of Ishmael, Abraham had clung tenaciously to the hope that this son might be the promised heir. Blind to the possibility of Sarah’s presenting him with a son, at her advanced age, Abraham intercedes on behalf of Ishmael. Abraham would be content to accept him, the son of his own devising, in lieu even of the one to be born of Sarah. Furthermore, it would save him the embarrassment of giving up his publicly announced plan for Ishmael to be his heir (see PP 146).