Musnad Ahmad 28:490

Hadba narrated to us, Hammam narrated to us, he said: Qatadah was asked about the one who approaches his wife in her anus. Qatadah said: ‘Amr ibn Shu’ayb narrated to us, from his father, from his grandfather, that the Prophet, peace and blessings of Allah be upon him, said: “It is the minor sodomy.” Qatadah said: And ‘Uqbah ibn Wasaj narrated to me, from Abu al-Darda’, who said: “And does anyone do that except a disbeliever?”