Leviticus 11:34
Of all meat which may be eaten, that on which such water cometh shall be unclean: and all drink that may be drunk in every such vessel shall be unclean. Of all meat which may be eaten, that on which such water cometh shall be unclean: and all drink that may be drunk in every such vessel shall be unclean.
The verse carries the distinction between clean and unclean into everyday eating and drinking, for food that may be eaten becomes unclean when water coming from a vessel made unclean by an unclean creature comes upon it, and all drink that may be drunk in every such vessel becomes unclean in the same way. It belongs to the law of Moses, God's food laws for Israel and the Hebrews, which forbid eating the flesh of animals, birds, and fish declared unclean and unfit for food, including swine's flesh and the flesh of certain other animals, while even meats that are permitted are placed under careful limits. Those food and drink restrictions were given to protect the health and life of God's people, because the forbidden meats are hurtful and not the best food, filling the blood with impurities and shortening life, and enfeebling brain and muscle while imperiling physical and moral powers instead of keeping mind and physical structure in the very best health for God's service.
Swine's flesh in particular fills the system with humors and in that warm climate often produced leprosy, acting far more injuriously there than in a colder climate, and swine were never designed to be eaten under any circumstances but to run free as scavengers devouring decaying substances that would otherwise poison the atmosphere and thus preserve health. Submission to these wise prohibitions would have removed everything injurious to health so that no sickness would have been among Israel, while refusal to submit left the people to the food they lusted for. The restrictions were not a command to strain all drinking water for tiny, unseen insects, specks, or the smallest creature that might be classed with unclean animals, and to require this went beyond what God specified and perverted the law.
That added straining turned a health law into a trivial, burdensome exaction that kept people anxious about ritual uncleanness while great sins were committed. Daniel's refusal of the king's food shows these dietary requirements remained binding on him in Babylon, since the food appointed to Daniel and his companions at the king's table included such unclean meats along with wine. Daniel and his companions refused that food and practiced temperance in eating and drinking to keep mental powers clear and undimmed, to perfect character and intellect, to honor God and stand as representatives of true religion, making God's will the supreme law of life while trusting God and making decided efforts to resist temptation.