Leviticus 27:31-35

If, therefore, someone should ever want to redeem part of his tithe, he shall add to it a fifth of it.

For every tenth part of herd or flock, whatever passes under the rod, the tenth one shall be holy to the Lord.

He is not to be concerned whether it is good or bad, nor shall he exchange it; yet if he does exchange it, then both it and its substitute shall become holy. It shall not be redeemed.’ ”

These are the commandments which the Lord commanded Moses for the sons of Israel on Mount Sinai.