Abd al-Wahhab bin Ata (may Allah have mercy on him) said: I asked Sa'id (may Allah have mercy on him) about a man who has intercourse with his wife in her backside, and he narrated to us from Qatadah (may Allah have mercy on him), from Uqbah (may Allah have mercy on him), from Sayyiduna Abu al-Darda' (may Allah be pleased with him): "Only a disbeliever does that."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14131