Sahih al-Bukhari, Hadith 5232 ⓘ

Narrated `Uqba bin 'Amir: Allah's Messenger said, "Beware of entering upon the ladies." A man from the Ansar said, "Allah's Apostle! What about Al-Hamu the in-laws of the wife (the brothers of her husband or his nephews etc.)?" The Prophet replied: The in-laws of the wife are death itself.

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ أَبِي الْخَيْرِ، عَنْ عُقْبَةَ بْنِ عَامِرٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ إِيَّاكُمْ وَالدُّخُولَ عَلَى النِّسَاءِ ‏"‏‏.‏ فَقَالَ رَجُلٌ مِنَ الأَنْصَارِ يَا رَسُولَ اللَّهِ أَفَرَأَيْتَ الْحَمْوَ‏.‏ قَالَ ‏"‏ الْحَمْوُ الْمَوْتُ ‏"‏‏.‏