Leviticus 5:2-3

²Or if a soul shall touch any unclean thing, whether a carcass of an unclean beast, or a carcass of unclean cattle, or the carcass of unclean creeping animals, and it shall be hidden from him; he also shall be unclean, and guilty.

³Or if he shall touch the uncleanness of man, whatever uncleanness it may be that a man shall be defiled with, and it be hid from him; when he knoweth of it , then he shall be guilty.