Religious restrictions on the consumption of pork

Religious restrictions on the consumption of pork are a common food taboo, particularly in the Middle East among Jews and Muslims. Swine were prohibited in ancient Syria and Phoenicia, and the pig and its flesh represented a taboo observed, Strabo noted, at Comana in Pontus. A lost poem of Hermesianax, reported centuries later by the traveller Pausanias, reported an etiological myth of Attis destroyed by a supernatural boar to account for the fact that "in consequence of these events the Galatians who inhabit Pessinous do not touch pork". Concerning Abrahamic religions, clear restrictions exist in Jewish dietary laws (Kashrut) and in Islamic dietary laws (Halal).
Although Christianity is also an Abrahamic religion, most of its adherents do not follow these aspects of Mosaic law and are permitted to consume pork. However, Seventh-day Adventists consider pork taboo, along with other foods forbidden by Jewish law. The Eritrean Orthodox Church and the Ethiopian Orthodox Church do not permit pork consumption, while in the Balkans lard is considered inpure. Hebrew Roots Movement adherents also do not consume pork.
Many Yazidis in Kurdistan regard pork as forbidden.
Prohibitions in Jewish law.
The Torah (Pentateuch) contains passages in Leviticus that lists the animals people are permitted to eat. It first notes what qualifies an animal that is absolutely permitted:
Animals that have cloven hooves and chew their cud are ruminants such as cows, sheep, and deer. This text does not specify every possible animal by name, only their behaviors. 
The text goes on to describe specific animals that are known and meet one, but not both, of those qualifications, thereby prohibiting their consumption. It does not elaborate on the exact reason for prohibition other than physical characteristics. 
Pigs are described in this section as prohibited because they have a cloven hoof but don't chew their cud.
Deuteronomy expands on the list of permitted animals.
Deuteronomy reiterates what Leviticus states on pigs.
Prohibitions in Islamic law.
One example of verses from the Quran on pig consumption:
I do not find in what has been revealed to me anything forbidden for anyone who wants to eat unless it is carrion, outpoured blood and the flesh of swine, all of which is unclean (Quran Al An'am 6:145)
The prohibition of certain food is also linked to Islamic Cosmology. Accordingly "good" and "evil" qualities are transferred by eating an object carrying a certain quality, that also affects the soul of human, the pig rendered with "evil qualities". Moreover, there is a story that says pigs were created to eat wastes. This was during the period of prophet Noah’s flood. All the wastes on the ship were eaten by this animal. This is another reason why this animal is said to be unclean.
Other.
According to Herodotus, The Scythians had a taboo against the pig, which was never offered in sacrifice, and apparently the Scythians were loath to so much as keep swine within their lands.
Scottish pork taboo was Donald Alexander Mackenzie's phrase for discussing an aversion to pork among Scots, particularly Highlanders, which he believed stemmed from an ancient taboo. Several writers who confirm that there was a prejudice against pork, or a superstitious attitude toward pigs, do not see it in terms of a taboo related to an ancient cult. Any prejudice is generally agreed to have disappeared by 1800.
Interpretations of restrictions.
The cultural materialistic anthropologist Marvin Harris thinks that the main reason for prohibiting consumption of pork was ecological-economical. Pigs require water and shady woods with seeds, but those conditions are scarce in the Middle East. Unlike many other forms of livestock, pigs are omnivorous scavengers, eating virtually anything they come across, including carrion and refuse, which was deemed unclean. Furthermore, a Middle Eastern society keeping large stocks of pigs could destroy their ecosystem.
It is speculated that chickens supplanted pigs as a more portable and efficient source of meat, and these practical concerns led to the religious restrictions.
Maimonides, the Jewish philosopher, legal codifier, and court physician to the Muslim sultan Saladin in the 12th century, understood the dietary laws chiefly as a means of keeping the body healthy. He argued that the meat of the forbidden animals, birds, and fish is unwholesome and indigestible. According to Maimonides, at first glance, this does not apply to pork, which does not appear to be harmful. Yet, Maimonides observes, the pig is a filthy animal, and if swine were used for food, marketplaces and even houses would be dirtier than latrines.
Rashi (the primary Jewish commentator on the Bible and Talmud) lists the prohibition of pig as a law whose reason is not known, and may therefore be derided by others as making no sense.
The Chinuch Sefer HaChinuch (an early work of Halachah) gives a general overview of the Jewish dietary laws. He writes "And if there are any reasons for the dietary laws which are unknown to us or those knowledgeable in the health field, do not wonder about them, for the true Healer that warns us against them is smarter than us, and smarter than the doctors."