Leviticus 11:24

And for these ye shall be unclean: whosoever toucheth the carcase of them shall be unclean until the even.

Leviticus 11:24 belongs to the health and sanitary laws taught to Israel in the wilderness as training before entering Canaan, distinguishing animals pronounced unclean from those permitted for food. The law forbids eating any unclean thing, including swine's flesh and the flesh of certain other animals and unclean beasts. Related dietary rules barred eating animals that had died on their own, required permitted animals to be healthy and properly drained of blood, and forbade fat and blood. The rule that whoever touches their carcass shall be unclean until the evening belongs to this same law.

These restrictions were not an arbitrary exercise of authority but were given to preserve life and health by guarding against impurity and harm and by keeping the blood pure through simple, healthful food. Unclean meat is hurtful and not the best food because it fills the blood with impurities and the system with humors and shortens life. Swine's flesh in that warm climate often produced leprosy and its influence there was far more injurious than in a colder climate, yet swine were never designed to be eaten under any circumstances. Swine were useful as scavengers where much decayed upon the ground, devouring decaying substances that would poison the atmosphere as a means of preserving health.

If Israel had submitted to these wise prohibitions, God would have removed from them everything injurious to health and allowed no sickness among them. Daniel and his companions excluded meats of this unclean class from their diet to preserve health and clear minds for God's service, since eating swine's flesh and the other forbidden meats would defile him. Intemperance in eating and drinking and indulgence of base passions benumbs the fine sensibilities, so that when appetite controls reason sacred things are placed on a level with common things and are not discerned.

The Pharisees perverted this law and extended it beyond what God required into burdensome traditions and minute ceremonies about ritual purity, requiring the people to strain all water used for drinking lest it contain the smallest insect that might be classed with the unclean animals. That trivial exaction kept people anxious about ritual purity and distracted them from true religion, and it is contrasted with the magnitude of their actual sins as straining out a gnat while swallowing a camel.