The idea that dogs are unclean is based on hadiths such as these:
“Once Gabriel promised the Prophet (that he would visit him, but Gabriel did not come) and later on he said, ‘We, angels, do not enter a house which contains a picture or a dog.’” — Sahih Bukhari 4.54.50
“Abdullah (b. Umar) (Allah be pleased with them) reported: Allah’s Messenger (may peace be upon him) ordered the killing of dogs and we would send (men) in Medina and its corners and we did not spare any dog that we did not kill, so much so that we killed the dog that accompanied the wet she-camel belonging to the people of the desert.” — Sahih Muslim 3811
The idea that Sharia actually allows for guide dogs is based on this hadith:
“Ibn Mughaffal reported: The Messenger of Allah (may peace be upon him) ordered killing of the dogs, and then said: What about them, i. e. about other dogs? and then granted concession (to keep) the dog for hunting and the dog for (the security) of the herd, and said: When the dog licks the utensil, wash it seven times, and rub it with earth the eighth time.” — Sahih Muslim 551
“Blind man sues Arab restaurant for rejecting guide dog entry, Sharia law,” Jerusalem Post, February 19, 2021:
A blind Arab man sued a restaurant that refused to allow him to enter accompanied by a guide dog, according to a press statement from the Commission on the Rights of Persons with Disabilities. The lawsuit asserts that refusal to allow the guide dog to enter goes against Sharia law.
Islamic law expert Dr. Ihab Sharif submitted his opinion to a Magistrate’s Court in Netanya on behalf of the Equal Rights Commission for Persons with Disabilities, stated that Islamic law (Sharia) has a positive view of guide dogs. A guide dog is a vital need for a blind person and therefore, according to Sharia, he is allowed to own such a dog and society should allow him to enter with his dog in public places, including mosques.
Yet, the restaurant owner claimed that the dog is considered an unclean animal according to Islamic Sharia, so despite his vitality to the blind man who tried to enter the restaurant with him, he refused to allow it….