عَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ: سَمِعْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ يَقُولُ: ((مَنْ تَرَكَ مَوْضِعَ شَعْرَةٍ مِنْ جَنَابَةٍ لَمْ يُصِبْهَا مَاءٌ فَعَلَ اللَّهُ بِهِ كَذَا وَكَذَا مِنَ النَّارِ)) قَالَ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ: فَمِنْ ثَمَّ عَادَيْتُ شَعْرِي، زَادَ فِي رِوَايَةٍ: كَمَا تَرَوْنَ
It is narrated from Sayyiduna Ali (may Allah be pleased with him), he says: I heard the Noble Prophet (peace and blessings be upon him) say: Whoever, during the ritual bath of janabah, leaves an area equal to a single hair such that water does not reach it, Allah the Exalted will deal with him with the fire of Hell in such and such a manner. Sayyiduna Ali (may Allah be pleased with him) said: This is the reason I have enmity with my hair, as you can see.