Parashas Shemos
וַתֹּ֣אמֶר אֲחֹתוֹ֮ אֶל־בַּת־פַּרְעֹה֒ הַאֵלֵ֗ךְ וְקָרָ֤אתִי לָךְ֙ אִשָּׁ֣ה מֵינֶ֔קֶת מִ֖ן הָעִבְרִיֹּ֑ת וְתֵינִ֥ק לָ֖ךְ אֶת־הַיָּֽלֶד׃
Then his sister said to Pharaoh’s daughter, “Shall I go and get you a Hebrew nurse to suckle the child for you?”
Torah Temimah points to Sotah 12b (verified).
מינקת מן העבריות — מאי שנא מן העבריות? מלמד שהחזירוהו על כל המצריות לינק ולא ינק.
English: “A wet-nurse from the Hebrew women” — why specifically from the Hebrew women? This teaches that they passed him among all the Egyptian women to nurse and he would not nurse.
Custom
Chazal teach that Moshe refused all Egyptian wet-nurses, preserving the purity of the mouth that would later speak with God.