All traditional societies have food prohibitions. Often the cause of the prohibition defies logical explanation, but generally there is a deep belief that eating of the prohibited food will cause harm or offence not just in the human situation but in a spiritual sense. When we look at the Israelite list of creatures which may not be eaten, we find no scientific explanations for the ban on them. Eating of these animals was believed, in some way or other, to cause unholiness in the eater and so to separate him from God. Even touching 'unclean' creatures, alive or dead; caused a man to be affected and to require purification.

In the opening words of the chapter Aaron, as well as Moses, is given responsibility for seeing that the people observe the prohibitions. In Leviticus 10: 10 the priest is given the responsibility of distinguishing between holy and unholy, 'clean' and 'unclean'.