Leviticus 27:11

And if it is any unclean animal that may not be offered as an offering to the Lord , then he shall stand the animal before the priest ,

If what they vowed is a ceremonially unclean animal—one that is not acceptable as an offering to the Lord—the animal must be presented to the priest,

And if it be any unclean beast, of which they do not offer a sacrifice unto the Lord, then he shall present the beast before the priest :