Leviticus 5:1-2

“If anyone sins in that he hears a public adjuration to testify, and though he is a witness, whether he has seen or come to know the matter, yet does not speak, he shall bear his iniquity; or if anyone touches an unclean thing, whether a carcass of an unclean wild animal or a carcass of unclean livestock or a carcass of unclean swarming things, and it is hidden from him and he has become unclean, and he realizes his guilt