Musannaf Ibn Abi Shayba 9:900

Abu Khalid al-Ahmar narrated to us, from al-Dahhak bin Uthman, from Makhrama bin Sulayman, from Kurayb, from Ibn Abbas, who said: The Messenger of Allah (peace be upon him) said: "Allah does not look at a man who approaches a man or a woman in her anus."