"Jibril, peace be upon him, asked permission to enter upon the Prophet and he said: 'Come in.' He said: 'How can I come in when there is a curtain in your house on which there are images? You should either cut off their heads or make it into a rug to be stepped on, for we Angels do not enter a house in which there are images.'"
Sunan an-Nasa'i Book 48, Hadith 326