Musnad Ahmad 1130:1

'Abd al-Razzaq narrated to us, Ma'mar informed us, from 'Asim ibn Sulayman, from Muslim ibn Salam, from 'Isa ibn Hattan, from 'Ali ibn Talq, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "If one of you passes gas, let him perform ablution. And do not approach women in their posteriors, for Allah is not ashamed of the truth."