Musannaf Ibn Abi Shayba 9:907

Abu Usama narrated to us, from al-Walid ibn Kathir, who said: Ubayd Allah ibn Abd Allah ibn al-Husayn al-Khatmi narrated to us, from Abd al-Malik ibn Qays al-Khatmi, from Haram ibn Abd Allah, who said: I heard Khuzayma ibn Thabit saying: 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."