Musannaf Ibn Abi Shayba 9:909

Ibn Numayr narrated to us, from al-Salt ibn Bahram, from Abd al-Rahman ibn Mas’ud, from Abu al-Mu’tamir or Abu al-Juwayriyah, who said: Ali called out from the pulpit and said: "Ask me." A man said: "Is it permitted to approach women in their posteriors?" He said: "You have become base, may God make you base. Do you not see that God, the Exalted, says: 'Do you commit the abomination?'"