Leviticus 11:26
The carcases of every beast which divideth the hoof, and is not clovenfooted, nor cheweth the cud, are unclean unto you: every one that toucheth them shall be unclean. The carcases of every beast which divideth the hoof, and is not clovenfooted, nor cheweth the cud, are unclean unto you: every one that toucheth them shall be unclean.
The carcasses of every beast that divides the hoof yet is not fully cloven-footed and does not chew the cud are unclean, and everyone who touches them becomes unclean. The requirement belongs to the law given through Moses to Israel, part of the sanitary and dietary laws and the health principles taught during the wilderness training that placed animal food under careful restrictions. The law forbids Israel to eat unclean meats as unfit for food, including swine's flesh and the flesh of certain other animals that lack the required combination of cloven hoof and chewing the cud.
The restriction was given for health and was not arbitrary, for the forbidden flesh is hurtful and not the best food, filling and polluting the blood with impurities and shortening life, while the law sought to protect life and health through simple, healthful food that keeps the blood pure. Swine in particular were never designed to be eaten under any circumstances, for their flesh fills the system with humors and in that warm climate often produced leprosy, acting far more injuriously there than in a colder climate. Swine were useful as scavengers allowed to run free in a fruitful country to devour decaying substances on the ground that would poison the atmosphere, thus preserving health.
If Israel had submitted to these wise prohibitions, everything injurious to health would have been removed from them and no sickness would have been allowed among them, but because they would not submit they were given what they lusted for. The meats offered at the king's table included foods this law pronounced unclean, and Daniel remained faithful to the law rather than defile himself with the king's food. Later teachers did not leave the restriction as given but went beyond it into unwarranted extremes and burdensome ceremonies, requiring the people to strain all water used lest it contain the smallest insect that might be classed with the unclean animals, which distracted from true religion. Jesus exposed these trivial outward exactions as blindness compared with the magnitude of their actual serious sins.