Musnad Ahmad 30:1942

Aswad ibn Amir narrated to us, Isra'il narrated to us, Abu Ishaq narrated to us, from Mujahid, from Abu Hurayrah, who said: Gabriel, peace be upon him, came to the Prophet, may Allah bless him and grant him peace, and said: "I came last night, and nothing prevented me from entering upon you except that there was an image in the house, or a dog."