Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) ordered us to kill dogs, 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) stopped us and said: "Now kill only the pure black dog with two spots on its head, for it is a devil."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11035