The Book of Menstruation
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَأَبُو كُرَيْبٍ قَالاَ حَدَّثَنَا وَكِيعٌ، عَنْ مِسْعَرٍ، عَنْ وَاصِلٍ، عَنْ أَبِي وَائِلٍ، عَنْ حُذَيْفَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم لَقِيَهُ وَهُوَ جُنُبٌ فَحَادَ عَنْهُ فَاغْتَسَلَ ثُمَّ جَاءَ فَقَالَ كُنْتُ جُنُبًا . قَالَ " إِنَّ الْمُسْلِمَ لاَ يَنْجُسُ " .Hudhaifa reported:The Messenger of Allah (ﷺ) happened to meet him and he was (sexually) defiled, and he slipped away and took a bath and then came and said: I was (sexually) defiled. Upon this he (the Holy Prophet) remarked: A Muslim is never defiled
From Sahih Muslim, whose reports the scholars accept as authentic.