Parashas Shemos · Passuk 1:22
וַיְצַ֣ו פַּרְעֹ֔ה לְכׇל־עַמּ֖וֹ לֵאמֹ֑ר כׇּל־הַבֵּ֣ן הַיִּלּ֗וֹד הַיְאֹ֙רָה֙ תַּשְׁלִיכֻ֔הוּ וְכׇל־הַבַּ֖ת תְּחַיּֽוּן׃ {פ}
Then Pharaoh charged all his people, saying, “Every boy that is born you shall throw into the Nile, but let every girl live.”
Torah Temimah points to Sotah 12a (verified).
היאורה תשליכוהו — ראו אצטגניני פרעה שמושיען של ישראל במים הוא לוקה, עמדו וגזרו כל הבן הילוד היאורה תשליכוהו. כיון דשדיוהו למשה, אמרו תו לא חזינן בההוא סימנא ובטלו לגזירתייהו, והם אינם יודעים שעל מי מריבה הוא לוקה.
English: “Into the Nile you shall cast him” — Pharaoh’s astrologers saw that the redeemer of Israel would be struck through water; they arose and decreed that every son born should be cast into the Nile. Once Moshe was thrown in, they said, “We no longer see that sign,” and they annulled their decree — but they did not know that he would be struck at the waters of Merivah.
Custom — historical etiology of the Nile decree.
Chazal teach that the decree of drowning was prompted by a partial vision of the redeemer’s future connection to water, a vision that was misread both in timing and in location.