Leviticus 5:1-2

‘If a person sins in hearing the utterance of an oath, and is a witness, whether he has seen or known of the matter—if he does not tell it, he bears guilt. ‘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.