Leviticus 22:1-9

Then the LORD spoke to Moses, saying, “Tell Aaron and his sons to be careful with the holy things (offerings, gifts) which the children of Israel dedicate to Me, so that they do not profane My holy name; I am the LORD. Say to them, ‘Any one of your descendants throughout your generations who approaches the holy things which the Israelites dedicate to the LORD, while he is [ceremonially] unclean, that person shall be cut off from My presence and excluded from the sanctuary; I am the LORD. No man of the descendants of Aaron who is a leper or has a discharge may eat the holy things [the offerings and the showbread] until he is clean. And whoever touches any person or thing made unclean by contact with a corpse or a man who has had a seminal emission, or whoever touches any crawling thing by which he is made unclean, or any person by whom he is made unclean, whatever it may be, [Lev 11:24-28] the person who touches any such thing shall be unclean until evening and shall not eat the holy things unless he has bathed his body in water. [Heb 10:22] When the sun sets, he will be clean, and afterward he may eat the holy things, for it is his food. He shall not eat that which dies [of natural causes] or is torn by a predator, becoming unclean by it; I am the LORD. Therefore the priests shall observe My ordinance, so that they will not bear sin because of it and die if they profane it; I am the LORD who sanctifies them.