וַיְצַ֣ו פַּרְעֹ֔ה לְכָל־עַמּ֖וֹ לֵאמֹ֑ר כָּל־הַבֵּ֣ן הַיִּלּ֗וֹד הַיְאֹ֙רָה֙ תַּשְׁלִיכֻ֔הוּ וְכָל־הַבַּ֖ת תְּחַיּֽוּן׃ (ס)
And Pharaoh charged all his people, saying: ‘Every son that is born ye shall cast into the river, and every daughter ye shall save alive.’
Mishnah Nedarim
One who vows [not to benefit] from those born may [benefit] from those to be born; from those to be born, he may not [benefit] from those born. Rabbi Meir permits [him to benefit] even from those to be born; But the Sages say: he meant all whose nature it is to be born.