Rashi on Genesis 36:3/רש"י על בראשית ל״ו:ג׳

1בשמת בת ישמעאל BASE-MATH ISHMAEL’S DAUGHTER — But elsewhere (28:9) she is called Mahalath! We find in the Agadic Midrash on the Book of Samuel (Ch. 17) that there are three classes whose sins are pardoned: a proselyte, one who is exalted to a high position and a man on his marriage. It derives the proof for the latter case from here; viz., the reason why she was also calleth Mahalath (pardon) was because his (Esau’s) sins were pardoned on his marriage to her (Megillah 17a; cf. also Genesis Rabbah 63).

2אחות נביות SISTER OF NEBAIOTH — because he gave her in marriage after Ishmael’s death she is called after his name (Nebaioth’s sister).