عَنْ خُزَيْمَةَ بْنِ ثَابِتٍ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ إِنَّ اللَّهَ لَا يَسْتَحْيِي مِنَ الْحَقِّ لَا تَأْتُوا النِّسَاءَ فِي أَدْبَارِهِنَّ
It is narrated from Sayyiduna Khuzaymah bin Thabit (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Verily, Allah does not shy away from the truth. Do not approach women from the back (i.e., do not have unnatural intercourse with them).