Leviticus 27:32-34

³²As for every tenth of the herd or the flock, whatever passes under the shepherd's rod, one-tenth must be set apart to Yahweh.

³³The shepherd must not search for the better or the worse animals, and he must not substitute one for another. If he changes it at all, then both it and that for which it is changed will be holy. It cannot be redeemed.'”

³⁴These are the commandments that Yahweh gave at Mount Sinai to Moses for the people of Israel.