Leviticus 5:2-3

‘Or if a person touches any unclean thing, whether it is the carcass of an unclean beast, or the carcass of unclean livestock, or the carcass of unclean creeping things, and he is unaware of it, he also shall be unclean and guilty. Or if he touches human uncleanness—whatever uncleanness with which a man may be defiled, and he is unaware of it—when he realizes it, then he shall be guilty.