Dog in Farsi is Saag. The majority of Muslim jurists consider dogs to be ritually unclean. However, outside their ritual uncleanness, Islamic fatâwâ, or rulings, enjoin that dogs be treated kindly or else be freed.
Muslims generally cast dogs in a negative light because of their ritual impurity. The story of the Seven Sleepers of Ephesus in the Qur'an (and also the role of the dog in early Christianity) is one of the striking exceptions. Muhammad didn't like dogs according to Sunni tradition, and most practicing Muslims do not have dogs as pets. It is said that angels do not enter a house which contains a dog. Though dogs are not allowed for pets, they are allowed to be kept if used for work, such as guarding the house or farm, or when used for hunting purposes.
According to a generally unaccepted Sunni tradition attributed to Muhammad, black dogs are evil, or even devils, in animal form. This report reflects the pre-Islamic Arab mythology and the vast majority of Ulema (Muslim jurists) viewed it to be falsely attributed to Muhammad.
Another Sunni tradition attributed to Muhammad commands Muslims not trade or deal in dogs. According to El Fadl, this shows the cultural biases against dogs as a source of moral danger. However, the Hanafi scholars, the largest school of ritual law in Sunni Islam, allow all trading in dogs.
According to one story, Muhammad is said to have informed a prostitute who had seen a thirsty dog hanging about a well and given it water to drink, that Allah forgave her because of that good deed.
In a tradition found in the Sunni hadith book, al-Muwatta, Muhammad states that the company of dogs voids a portion of a Muslim’s good deeds.
Dogs, outside the ritual legal discourse, were often portrayed in the literature as a symbol of highly esteemed virtues such as self-sacrifice and loyalty or on the other hand as an oppressive instrument in the hands of despotic and unjust rulers.

en.wikipedia.org/wiki/Islam_and_animals#Dogs