Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) ordered us to kill dogs, so we killed them, to the extent that if a Bedouin woman came with her dog, we would kill it. Then the Messenger of Allah (peace and blessings be upon him) said: "Were it not that dogs are a nation among the nations, which I dislike to wipe out, I would have ordered that they be killed; but now kill only the pure black dog that has two white spots like eyes."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11034