Musnad Abu Ya'la al-Mawsili 110:51

Abu Bakr ibn Abi Shaybah narrated to us, Abu Khalid al-Ahmar narrated to us, from al-Dahhak ibn Uthman, from Makhramah ibn Sulayman, from Kurayb, from Ibn Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Allah does not look at a man who approaches a man or a woman in her anus."