וַיֹּ֨אמֶר אֱלֹהִ֜ים אֶל־אַבְרָהָ֗ם אַל־יֵרַ֤ע בְּעֵינֶ֙יךָ֙ עַל־הַנַּ֣עַר וְעַל־אֲמָתֶ֔ךָ כֹּל֩ אֲשֶׁ֨ר תֹּאמַ֥ר אֵלֶ֛יךָ שָׂרָ֖ה שְׁמַ֣ע בְּקֹלָ֑הּ כִּ֣י בְיִצְחָ֔ק יִקָּרֵ֥א לְךָ֖ זָֽרַע׃
Deus, porém, disse a Abraão: Não pareça isso duro aos teus olhos por causa do moço e por causa da tua serva; em tudo o que Sara te diz, ouve a sua voz; porque em Isaque será chamada a tua descendência.
Rashi on Genesis
שמע בקולה HEARKEN UNTO HER VOICE — we may infer that Abraham was inferior to Sarah in respect of prophecy (Exodus Rabbah 1:1).
Rashbam on Genesis
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.
Sforno on Genesis
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)