Bukhari

Narrated Abu Huraira: Allah's Apostle said, "If a dog drinks from the utensil of anyone of you it is essential to wash it seven times."

Narrated Abu Huraira: The Prophet said, "A man saw a dog eating mud from (the severity of) thirst. So, that man took a shoe (and filled it) with water and kept on pouring the water for the dog till it quenched its thirst. So Allah approved of his deed and made him to enter Paradise."

And narrated Hamza bin 'Abdullah: My father said. "During the lifetime of Allah's Apostle, the dogs used to urinate, and pass through the mosques (come and go), nevertheless they never used to sprinkle water on it (urine of the dog.)"

Narrated `Adi bin Hatim: I asked the Prophet (about the hunting dogs) and he replied, "If you let loose (with Allah's name) your tamed dog after a game and it hunts it, you may eat it, but if the dog eats of (that game) then do not eat it because the dog has hunted it for itself." I further said, "Sometimes I send my dog for hunting and find another dog with it. He said, "Do not eat the game for you have mentioned Allah's name only on sending your dog and not the other dog."