Mishkat al-Masabih
Mishkat al-Masabih 444
وَعَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ: أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنْ تَرَكَ مَوْضِعَ شَعَرَةٍ مِنْ جَنَابَةٍ لَمْ يَغْسِلْهَا فعل بهَا كَذَا وَكَذَا من النَّار» . قَالَ عَليّ فَمن ثمَّ عاديت رَأْسِي ثَلَاثًا فَمن ثمَّ عاديت رَأْسِي ثَلَاثًا فَمِنْ ثَمَّ عَادَيْتُ رَأْسِي ثَلَاثًا. (رَوَاهُ أَبُو دَاوُدَ وَأَحْمَدُ وَالدَّارِمِيُّ إِلَّا أَنَّهُمَا لَمْ يُكَرِّرَا: فَمن ثمَّ عاديت رَأْسِي)
ʿAlī reported that the Messenger of Allah said: ‘Whoever leaves even a hair’s breadth of sexual impurity unwashed will suffer such-and-such in the Fire.’ ʿAlī said: ‘For that reason I treated my head as an enemy’—and repeated this three times.
Abū Dāwūd, Aḥmad, and al-Dārimī transmitted it; Aḥmad and al-Dārimī did not repeat the phrase ‘For that reason I treated my head as an enemy.’