Parashas Bamidbar
וְנָתַתָּ֣ה הַכֶּ֔סֶף לְאַהֲרֹ֖ן וּלְבָנָ֑יו פְּדוּיֵ֕י הָעֹדְפִ֖ים בָּהֶֽם׃
and give the money to Aaron and his sons as the redemption price for those who are in excess.
Torah Temimah points to TT / Rambam parallel (verified).
ונתתה הכסף לאהרן ולבניו — פדיון הבן ניתן לזכרי כהונה.
English: “And you shall give the money to Aharon and his sons” — the redemption of the [human] firstborn is given to the males of the priesthood.
Custom
Chazal derive that the five-shekel redemption payment is given to male kohanim.