Leviticus 11:4
Nevertheless these shall ye not eat of them that chew the cud, or of them that divide the hoof: as the camel, because he cheweth the cud, but divideth not the hoof; he is unclean unto you. Nevertheless these shall ye not eat of them that chew the cud, or of them that divide the hoof: as the camel, because he cheweth the cud, but divideth not the hoof; he is unclean unto you.
This instruction belongs to the Mosaic law of health taught to Israel during wilderness training before entering Canaan and applied in Canaan, identifying certain animals as unclean and forbidden for food. An animal permitted for food had to meet both prescribed conditions, and meeting only one condition was insufficient. The camel is excluded and unclean not to be eaten because although it chews the cud it does not divide the hoof.
The prohibition was a wise health measure rather than arbitrary control, given because the forbidden animals are hurtful and unfit for food and not the best articles of food. It was given to preserve health and faculties by pure, simple food that keeps the blood pure, because eating such flesh fills the blood with impurities and shortens life. For example, swine's flesh fills the system with humors and in that warm climate often produced leprosy, being more injurious there than in a colder climate. Swine were never designed to be eaten under any circumstances but are useful as scavengers, permitted to run free to devour decaying substances that would poison the atmosphere and thus preserve health. If Israel had submitted to the prohibition, everything injurious to health would have been removed from them and no sickness would have been allowed among them.
The royal meats appointed to Daniel and his companions included foods pronounced unclean by this law. Daniel treated these dietary requirements as commands of the Lord, so that eating the forbidden meat would defile him, and therefore he refused the king's food. The limits did not justify adding unwarranted extremes, such as requiring all drinking water to be strained lest the smallest insect in it be classed with the unclean animals. Multiplying them into burdensome rules and ceremonies of external distinction kept people preoccupied with external distinctions and distracted them from true religion.
Against these trivial exactions of external cleanliness was set the magnitude of actual sins, as in Jesus calling the Pharisees blind guides who strain at a gnat and swallow a camel while neglecting the seriousness of their sins.