Allah's Messenger (ﷺ) ordered us to kill dogs, and we carried out this order so much so that we also kill the dog coming with a woman from the desert. Then Allah's Apostle (ﷺ) forbade their killing. He (the Prophet further) said: It is your duty the jet-black (dog) having two spots (on the eyes), for it is a devil.
Sahih Muslim Book 22, Hadith 59