Parashas Shemos · Passuk 1:8
וַיָּ֥קָם מֶֽלֶךְ־חָדָ֖שׁ עַל־מִצְרָ֑יִם אֲשֶׁ֥ר לֹֽא־יָדַ֖ע אֶת־יוֹסֵֽף׃
A new king arose over Egypt who did not know Yosef.
Torah Temimah points to Rav and Shmuel — Sotah 11a (verified).
פליגי רב ושמואל, חד אמר חדש ממש, וחד אמר שנתחדשו גזירותיו.
English: Rav and Shmuel disagree. One said [it was] a new [king] in the literal sense; the other said that his decrees were renewed.
Custom — dispute over the plain sense of “new” versus a midrashic reading of renewed decrees.
Chazal leave open whether a literally new Pharaoh arose or whether the existing ruler adopted a new, hostile policy. Either reading explains the sudden oppression.