Musannaf Ibn Abi Shayba 9:899

Abu Bakr narrated to us, from Hafs, from Asim, from Isa ibn Salam, from Ali ibn Talq, who said: I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: "Indeed, Allah is not ashamed of the truth. Do not approach women in their posteriors," or he said, "in their anuses."