Leviticus 5:2 NIV

2 “ ‘If anyone becomes aware that they are guilty—if they unwittingly touch anything ceremonially unclean (whether the carcass of an unclean animal, wild or domestic, or of any unclean creature that moves along the ground) and they are unaware that they have become unclean, but then they come to realize their guilt;

References for Leviticus 5:2