Pigs are described as unclean in Leviticus 11:7 and Deuteronomy 14:8. More generally, the classification of clean and unclean animals, and the related prescriptions, are found in Genesis 7:2-3; Leviticus 11 and Deuteronomy 14:3-21. See the altercation between Peter and an innkeeper in EMV 292.1.
Book of Leviticus 11, 7
Lv 11, 7 : Likethe swine, which has a divided horn and a cloven foot, but does not chew the cud: it will be unclean for you.
Deuteronomy 14, 8
Deut 14, 8: Like the swine, which has a divided horn but does not chew the cud: it shall be unclean for you. You shall not eat their flesh, nor touch their carcasses.
Book of Genesis 7, 2-3
Gn 7, 2-3 : Of all the clean animals, you shall take with you seven pairs, males and their females, and of all the animals that are not clean, you shall take two, a male and his female; seven pairs also of the birds of the air, males and their females, to keep alive their race on the face of all the earth.
Book of Leviticus 11
Lev 11: Yahweh spoke to Moses and Aaron, saying to them: "Speak to the children of Israel, and say:
These are the animals you shall eat of all the beasts that are on the earth: Every animal that has a divided horn and a cloven foot, and chews the cud, you shall eat. But you shall not eat those that only chew the cud, or that only have a divided horn. Such is the camel, which chews the cud, but whose horn is not divided: it will be unclean to you. Like the jerboa, which chews the cud, but whose horn is not divided: it will be impure for you. Like the hare, which chews the cud but does not have a divided horn: it will be unclean for you. Like the pig, which has a divided horn and a cloven foot, but does not chew the cud: it shall be unclean for you. 8You shall not eat their flesh, nor touch their carcasses: they shall be unclean for you.
These are the beasts you shall eat of all that are in the waters: whatever has fins and scales in the waters, whether in the sea or in the rivers, you shall eat. But everything that does not have fins and scales, in the seas and in the rivers, among all the animals that move in the waters and among all the living creatures that are in them, you will find an abomination. They shall be an abomination to you; you shall not eat their flesh, and their carcasses shall be an abomination to you. Everything in the waters that has no fins or scales is an abomination to you.
These are the birds you will abhor; they shall not be eaten, for they are an abomination: the eagle, the osprey and the vulture: the kite and all kinds of falcons; all kinds of ravens; the ostrich, the kite, the gull and all kinds of hawks; the owl, the cormorant and the owl; the swan, the pelican and the bearded vulture; the stork, all kinds of herons; the hoopoe and the bat.
Any winged insect that walks on four legs, you will abhor. But of all the winged insects that walk on four legs, you shall eat those that have legs above their legs, to leap on the earth. These are the ones you shall eat: every kind of locust, every kind of solam, every kind of hargol, every kind of hagab. Every other winged beast with four legs is an abomination to you.
These also shall make you unclean: whoever touches their dead body shall be unclean until the even, and whoever takes away any part of their dead body shall wash his clothes and be unclean until the even.
Any animal that has a divided horn, but is not forked-footed and does not chew the cud, will be unclean to you; whoever touches it will make himself unclean. And of the four-footed animals, everything that walks on the soles of its feet will be unclean to you: whoever touches their dead body will be unclean until evening; and whoever carries their dead body will wash his clothes and be unclean until evening. These animals will be unclean for you.
Among the little beasts that crawl on the earth, these are the ones that will be unclean for you: the weasel, the mouse and all kinds of lizards; the shrew, the chameleon, the salamander, the green lizard and the mole. These are the unclean reptiles for you: whoever touches them dead will be unclean until evening. Anything on which dead ones fall shall be unclean: wooden utensils, clothing, skins, sackcloth, anything you use; you shall put it in water, and it shall remain unclean until evening, after which it shall be clean. If any of it falls into the middle of any earthen vessel, everything in the middle of the vessel will be defiled, and you will break the vessel. Any foodstuff prepared with water will be defiled; any beverage used in any vessel will be defiled. Every object on which anything of their dead body falls will be defiled; the oven and the vessel with its lid will be destroyed; they will be defiled and you will hold them to be defiled. But the springs and cisterns, where the pools of water are formed, will remain pure; however, whoever touches the dead body will be unclean. If anything of their dead body falls on a seed that is to be sown, the seed will remain pure; but if water has been put on the seed, and anything of their dead body falls on it, you will hold it unclean.
If one of your food animals dies, whoever touches its corpse will be unclean until evening. Whoever eats of its dead body shall wash his clothes and be unclean until the evening; whoever carries its dead body shall wash his clothes and be unclean until the evening.
Every creeping thing that creeps on the earth is an abomination to you; it shall not be eaten. You shall not eat any animal that crawls on the ground, whether it be one that crawls on its belly, or one that walks on four feet or on many feet; for they are an abomination to you.
Do not make yourselves abominable by all these creeping things; do not make yourselves unclean by them; you will be defiled by them. For I am Yahweh, your God; you shall sanctify yourselves and be holy, for I am holy; and you shall not be defiled by all creeping things that creep upon the earth. For I am Yahweh, who brought you up out of the land of Egypt to be your God. You shall be holy, for I am holy. "This is the law for all four-footed animals, for birds, for every living thing that moves in the water, and for every creeping thing that crawls on the earth, so that you may distinguish between the unclean and the clean, between the animal that can be eaten and the animal that cannot be eaten.
Deuteronomy 14, 3-21
You shall not eat any abominable thing. These are the animals you may eat: the ox, the sheep and the goat; the stag, the gazelle and the fallow deer; the ibex, the antelope, the wild ox and the wild goat. You shall eat of every animal that has a divided horn and a cloven foot, and that chews the cud. But you shall not eat of those that only chew the cud, or that only have a divided horn and a cloven foot; such are the camel, the hare and the rabbit, which chew the cud but do not have a divided horn: they shall be unclean to you; such again is the pig, which has a divided horn but does not chew the cud: it shall be unclean to you. You shall not eat their flesh, nor touch their carcasses.
These are the animals you shall eat of all that are in the waters: you shall eat everything that has fins and scales; but everything that does not have fins and scales you shall not eat: it shall be unclean for you. You shall eat every clean bird. These are the ones you shall not eat: the eagle, the osprey and the vulture; the falcon, the kite and all kinds of goshawk; all kinds of raven; the ostrich, the owl, the gull and all kinds of sparrowhawk; the owl, the ibis and the owl; the pelican, the cormorant and the loon; 18the stork and all kinds of heron; the hoopoe and the bat. 19You shall regard every winged insect as unclean: it shall not be eaten. You must eat every pure bird. You shall not eat any dead animal. You shall give it to the stranger within your gates to eat, or sell it to a foreigner; for you are a people holy to Yahweh, your God. You shall not boil a kid in its mother's milk.