LXX Num 18:15

καὶ πᾶν διανοῖγον μήτραν ἀπὸ πάσης σαρκός, ἃ προσφέρουσιν κυρίῳ ἀπὸ ἀνθρώπου ἕως κτήνους, σοὶ ἔσται· ἁλλ’ ἢ λύτροις λυτρωθήσεται τὰ πρωτότοκα τῶν ἀνθρώπων, καὶ τὰ πρωτότοκα τῶν κτηνῶν τῶν ἀκαθάρτων λυτρώσῃ.

The firstborn of every womb, whether man or beast, that is offered to the LORD belongs to you. But you must surely redeem every firstborn son and every firstborn male of unclean animals.