Leviticus 27:30-34 ESV
“Every tithe of the land, whether of the seed of the land or of the fruit of the trees, is the LORD’s; it is holy to the LORD. If a man wishes to redeem some of his tithe, he shall add a fifth to it. And every tithe of herds and flocks, every tenth animal of all that pass under the herdsman’s staff, shall be holy to the LORD. One shall not differentiate between good or bad, neither shall he make a substitute for it; and if he does substitute for it, then both it and the substitute shall be holy; it shall not be redeemed.”
These are the commandments that the LORD commanded Moses for the people of Israel on Mount Sinai.
ESV: English Standard Version 2016