Leviticus 27:32-34

³²And a tenth part of the herd and of the flock, whatever goes under the rod of the valuer, will be holy to the Lord.

³³He may not make search to see if it is good or bad, or make any changes in it; and if he makes exchange of it for another, the two will be holy; he will not get them back again.

³⁴These are the orders which the Lord gave to Moses for the children of Israel in Mount Sinai.