Musnad Ahmad 1130:3

'Abd al-Razzaq narrated to us, Sufyan informed us, from 'Asim, from 'Isa ibn Hattan, from Muslim ibn Salam, from 'Ali ibn Talq, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade that women be approached in their posteriors, for Allah is not ashamed of the truth.