Sahih al-Bukhari 640
Narrated Abu Huraira:
Once Iqama was pronounced and the people had straightened the rows, Allah's Messenger (ﷺ) went forward 
(to lead the prayer) but he was Junub, so he said, "Remain in your places." And he went out, took a 
bath and returned with water trickling from his head. Then he led the prayer.
حَدَّثَنَا إِسْحَاقُ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، قَالَ حَدَّثَنَا الأَوْزَاعِيُّ، عَنِ الزُّهْرِيِّ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ أُقِيمَتِ الصَّلاَةُ فَسَوَّى النَّاسُ صُفُوفَهُمْ، فَخَرَجَ رَسُولُ اللَّهِ صلى الله عليه وسلم فَتَقَدَّمَ وَهْوَ جُنُبٌ ثُمَّ قَالَ ‏
"‏ عَلَى مَكَانِكُمْ ‏"‏‏.‏ فَرَجَعَ فَاغْتَسَلَ ثُمَّ خَرَجَ وَرَأْسُهُ يَقْطُرُ مَاءً فَصَلَّى بِهِمْ‏.‏