In biblical literature, the operational distinction between clean and unclean animals is established long before the formal revelation of the Mosaic dietary laws at Mount Sinai.
Within the Genesis account of Noah's Flood, God directly commands Noah to gather seven pairs of every clean animal and only one pair of every unclean animal onto the Ark. This narrative indicates that early biblical figures possessed an innate understanding of which specific creatures were approved for divine sacrificial offerings and human survival.