Leviticus 27:10

27:10 He must not replace or exchange it, good for bad or bad for good, and if he does indeed exchange one animal for another animal, then both the original animal and its substitute will be holy.

Leviticus 27:33

27:33 The owner must not examine the animals to distinguish between good and bad, and he must not exchange it. If, however, he does exchange it, both the original animal and its substitute will be holy. It must not be redeemed.’”