Dietary laws are laws indicating which foods or combinations of foods may be eaten or must be abstained from, according to certain religious principles. Although such laws are generally associated with the Jewish tradition, their origin is pre-Israelitic, and their practice was known to the ancient Babylonians, Egyptians, and Hindus. Most scholars are convinced that the dietary laws of the Old Testament, known as Kashrut, were established to stress holiness, discipline, or moral sensitivity, rather than for hygienic reasons. They identify which foods are kosher, or suitable for eating; forbidden foods are known as trayfah, or unfit, a term originally referring to an animal that had been torn apart by predatory beasts. The laws are specifically described in Deuteronomy 14. Listed among the "abominable" or "unclean" foods are fish without scales or fins (such as shellfish), birds of prey, insects, and reptiles. Among mammals, only those that have cloven hoofs and chew their cud are permitted; hares and pigs are among the animals specifically forbidden.
The laws of the Kashrut dictate not only which animals may be eaten but the method of slaughter as well. The animal must be killed by an expertly trained and religiously observant Jew (a shohet), using a clean, sharp knife to sever the animal's windpipe with a single stroke. Blood, as a symbol of life, cannot be eaten, and is to be drained out of the animal; traces of blood are removed by washing and salting. Animals that die from natural causes or have been killed by wild beasts cannot be eaten, because of ethical considerations.
The commandment "You shall not boil a kid in its mother's milk" (Exodus 23:19) is thought to be the origin of the Talmudic prohibition against having meat and milk or milk products at the same meal. Meat and milk products are prepared in separate pots and served on dishes that are carefully differentiated. Foods that are designated as parue, or neutral, such as fish, eggs, vegetables, and fruits, can be eaten with either meat or dairy dishes.
Traditional Jews (Orthodox and Conservative) continue to follow the dietary commandments. Some Reform Jews consider them as a means of separation and tend to disregard them.
The New Testament rejected dietary laws as a means of separation or of establishing religious identity. In Mark 7:19, all foods are declared clean. Food laws have been retained, however, by certain Christian sects, as well as by Muslims. Other dietary laws, seemingly unrelated to those of the Old Testament though possibly also springing from an effort to instill holiness and discipline, are found throughout the world— among Hindus, for example.