בראשית כא:יב פירוש: רש״י, רשב״ם, ספורנו ורד״ק

שמע בקולה HEARKEN UNTO HER VOICE — we may infer that Abraham was inferior to Sarah in respect of prophecy (Exodus Rabbah 1:1).

יקרא לך זרע, a reference to the covenant between G’d and Avraham, which included that Avraham’s seed would remain strangers in a land not theirs before they would inherit the land of Canaan (15,13). G’d reminded him that his promise referred to Yitzchok and not to Ishmael.

אל ירע בעיניך על הנער ועל אמתך. כל אשר תאמר אליך שרה, do not be angry regarding anything that Sarah says to you concerning the lad and the maid, i.e. to expel them while they wear proof that they are slaves. Avraham’s having placed Ishmael’s on Hagar’s shoulder was a clear sign that Hagar was a slave woman who was charged with carrying Ishmael (verse 14)