It is narrated from Sayyiduna Ali (may Allah be pleased with him) that Hazrat Jibreel (peace be upon him) came to the service of the Prophet (peace and blessings be upon him) and said, "We do not enter a house in which there is a picture or a dog." At that time, there was a small dog belonging to Sayyiduna Hasan (may Allah be pleased with him) in the house.