Is it forbidden to feed dog in Islam?
According to the Hanafi school, if a dog touches one's clothes, one can perform prayers with those clothes on. Only, the saliva and the feces of the dog are najis (unclean).
There are hadiths (sayings of the Prophet) such as: “The angels of mercy do not enter those houses where there is a dog; certain merits for good deeds of the owner of such a house decrease each day; however, for such needs as hunting, looking after herds and guarding it is permitted to keep a dog.” Besides, as their saliva and hairs spread everywhere, it is possible for them to harm our prayers and health. For this reason, it is not right to keep a dog at home if there is no need. It is not forbidden to keep a dog at home even if there is no need, but it is lightly makrooh (abominable, though not forbidden).
On the other hand, one can live in a house where there is a dog, and the prayers and other religious activities performed are also valid, provided that the place or the rug where the prayer is done is clean.
Prophet Muhammad (peace and blessings be upon him) says: “A certain portion is decreased out of the merits (of good deeds) of a person who keeps dogs other than dogs of hunting, field, garden and herd.” (Bukhari, Zabaih, 6; Muslim, Musaqat, 46, 50, 56-58)
When the hadiths that inform that angels do not enter the houses where there is a dog, are taken into consideration, it is forbidden in Islam to keep dog in houses without such needs as security or hunting. This is because;
a) The poor and the needy are in more need of the care and expenses of those who have enough opportunities to keep a dog.
b) According to the established medical researches, there are many illnesses caused by dogs infecting humans.
c) Dogs scare and pester those passing by and guests. (Günlük Hayatımızda Helaller ve Haramlar, Hayreddin Karaman, İz Publishing)
The reason why angels do not enter houses with dogs is that they stink and eat unclean things. For this reason, the person who keeps a dog without any need is punished with being deprived of angels' presence at his/her house. (Nawawi, Sharhu'l-Muslim, Cairo 1347-49/1929-30, XIV, 84; Ayni, Umdatu'l-Qari, Cairo 1348, XV, 139)
What is essential in the Hanafi school is that dog itself is not unclean, as it is made use of in security and hunting. Pig, though, is unclean on its own. Pig is meant in the verse, in the Qur'an: “It is unclean.”
Only, the saliva and the feces of dog are najis (unclean). Other parts of its body are not compared to those. If it puts its mouth into a pot, the pot is washed for seven times. The Prophet said: “If a dog drinks from the cup of one of you, let him/her wash it for seven times.” In the hadith books of Ahmad and Muslim: “The cleaning for one of your cups in which a dog put its mouth is by washing it for seven times, the first of which is done with earth.” (Ahmad, Bukhari, Muslim)
According to the school of Maliki, whether it is the dog which is permitted to be kept such as for guarding and herds, or any dog, it is absolutely clean. Only, if it puts its mouth into something, according to the most known view, it is washed for seven times as a religious act. If it puts its foot or its tongue without moving it, or if its saliva falls in, there is no need to wash it.
According to the Shafii and the Hanbali schools, dogs, pigs and those born of them, their leftovers and feces are unclean. The things polluted with those are cleaned for seven times, one of them being with earth. Based on the previous hadith, given the uncleanness of its mouth, the remaining parts are already unclean, because the mouth is actually the cleanest part of it, as respiration takes place. (See İslam Fıkhı Ansiklopedisi, Prof. Dr. Vehbe Zuhayli)