And the thing was very displeasing in Abraham's sight because of his son.
All Commentaries on Genesis 21:11 Go To Genesis 21
John Chrysostom
AD 407
For her part, however, Sarah was not guilty of acting unreasonably; she acted even quite logically, so logically that even God agreed with the words she spoke. The patriarch, being affectionate and well disposed toward Ishmael, did not take kindly to her remarks. “This remark about his son … struck Abraham as severe.” It was not, you see, that he took much interest in Hagar; rather, he was well disposed toward his son for the reason that he was then still in his youth. Consider in this case, however … the extraordinary considerateness of the loving God: when he saw Sarah apparently having a human problem in being distressed by the parity of esteem of the children and Abraham not taking kindly to the expulsion of Ishmael and the maidservant. (After all, even if in his great restraint he did not take issue with Sarah, it still struck him as severe, that is, harsh, repugnant, and oppressive.) At that point, in fidelity to his characteristic loving kindness and wishing to strengthen the bonds of harmony between them, the Lord said to Abraham, “Don’t let the remark about the child and the maidservant strike you as severe. Whatever Sarah says to you, heed her.”