We are commanded to know the signs that distinguish the types of animals that it is forbidden to eat from the types that are permitted, as it says "And you shall distinguish between the clean animal and the unclean and between the unclean bird and the clean"¹; and it says "And to distinguish between the unclean and the clean and between the animal that may be eaten and the animal that may not be eaten".^2,a Anything that comes from a forbidden animal (milk, eggs, etc.) is forbidden.^b

An animal is permitted only if it has a divided hoof and chews the cud, as it says "And any animal that has a hoof and divides it into two parts and chews the cud... it you may eat, but this you may not eat..."³; there are ten permitted types (three domestic, seven wild).^4,c There are 24 forbidden types of birds, as it says "And these you shall abominate among the birds, they shall not be eaten", and it says "You may eat any clean bird"⁵; the sages characterized the permitted birds as those that do not pounce and eat and that have an extra toe or a crop or a gizzard that can be peeled by hand.^d All (flying) insects are forbidden except for eight types of locusts, as it says "Any flying swarming thing is unclean for you, they shall not be eaten".^6,e All water creatures are forbidden except for those having fin and scale, as it says "And they shall be an abomination for you; from their flesh you shall not eat", and it says "Anything in the water... that has fin and scale you may eat".⁷ For swarming water creatures there is a further prohibition based on "You shall not abominate yourselves with any swarming thing that swarms".^8,f All creatures that crawl on the land (reptiles, insects, etc.) are forbidden, as it says "And any swarming thing that swarms on the ground is an abomination, it shall not be eaten"⁹; they are forbidden even if they do not [visibly] procreate, as it says "And you shall not make yourselves unclean with any swarming thing that crawls on the ground".¹⁰ They are also forbidden if they grow in food and go out onto the ground, as it says "Of all the swarming things that swarm on the ground [you shall not eat for they are an abomination]"¹¹; but if they grow in food not attached to the ground or in a confined liquid and never leave it they are permitted.^g

b) Physical Condition

It is forbidden to eat a premature animal until it has lived seven days, or (rabbinically) to eat a fertilized egg until it hatches.^h It is forbidden to eat parts detached from a living animal or bird, as it says "And you shall not eat torn flesh in the field"¹²; and there is a special prohibition for entire limbs, as it says "You shall not eat the life with the flesh"¹³; and Noah was commanded "But flesh with its life, its blood, you shall not eat."^14,i

It is forbidden to eat a dead animal or bird if it was not properly slaughtered, as it says "You shall eat no carcass".¹⁵ It is forbidden to eat an animal or bird that has undergone certain injuries or illnesses even if it is slaughtered, as it says "And you shall not eat torn flesh in the field".¹² It is forbidden to eat or to derive benefit from an animal that has been condemned to death even if it is slaughtered, as it says "[The ox shall be stoned] and its flesh shall not be eaten".^16,j

c) Body Parts and Mixtures

It is forbidden to eat the blood of an animal or bird, as it says "And you shall eat no blood of bird or animal".¹⁷ It is forbidden to eat certain parts of the fat of a permitted domestic animal, as it says "You shall eat no suet of ox, sheep or goat"¹⁸; these animals can be distinguished from the wild ones by certain characteristics of their horns. It is forbidden to eat the sciatic nerve of a permitted animal [as it says "Therefore the children of Israel do not eat the sciatic nerve that is on the hollow of the thigh"].^19,k

It is forbidden to cook the meat of a permitted domestic animal in the milk of such an animal or to derive benefit from the resulting mixture, as it says "You shall not cook a kid in its mother's milk".²⁰ The sages forbade eating the meat of any permitted animal or bird cooked in the milk of any permitted animal. They also forbade eating meat and milk together even though they were not cooked together; situations where it is possible that they may be eaten together must be avoided.^l

d) Plant Prohibitions

Grain (wheat, barley, rye, oats or spelt) that takes root before the 16th of Nisan is forbidden until the end of that day (or when the Temple exists, until the omer sacrifice is brought), as it says "And you shall not eat bread or roasted or fresh grain [until that very day, until you have brought your sacrifice]".^21,m

If grain or vegetables grow near a vine it is forbidden to derive benefit from them, as it says "[You shall not plant your vineyard with a mixture] lest the increase of the seed that you have planted and the crop of the vineyard become holy".²² The sages extended this prohibition to all lands.ⁿ

It is forbidden to derive benefit from the fruit of a tree for three years after it is planted, as it says "And when you come to the land [and plant any food-bearing tree]... for three years its fruit shall be forbidden for you, it shall not be eaten".²³ By tradition, this prohibition applies to all lands. In the land of Israel the fruit of the fourth year must be redeemed before it can be eaten [as it says "And in the fourth year all its fruit shall be holy"²⁴; when the Temple exists it can be eaten in Jerusalem].^o

e) Other Prohibitions

It is forbidden to eat food from which heave-offerings or tithes have not yet been separated, as it says "And they shall not profane the holy things of the children of Israel which they raise up to Ha-Shem"²⁵ -- in other words, one should not treat food as profane if holy things which are destined to be separated from it have not yet been separated. In many cases holy things themselves cannot be eaten, as will be explained elsewhere.^p

It is forbidden to derive benefit from food that has been sacrificed to an idol, as it says "[Where are their gods...] who ate the fat of their sacrifices [and] drank the wine of their libations?"²⁶ The sages forbade drinking wine touched by any non-Jew (even if he is not an idolator) if it is wine that is fit for libation.^q

It is rabbinically forbidden to eat food cooked by a non-Jew if it is a type of food that is not eaten raw and is served at royal tables (e.g., meat, fish, eggs), or bread baked by a non-Jew, or his milk or cheese (because of the possibility that the milk comes from a forbidden animal or the cheese was made with prohibited rennet). Metal or glass eating utensils bought from a non-Jew require immersion.^r

It is forbidden to engage in disgusting or unhealthy eating practices, as it says "Do not abominate yourselves... but make yourselves holy, for I am holy".^27,s