Sahih al-Bukhari 143
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · Providing water at lavatories (for washing the private parts after answering the call of nature)
Narrated Ibn `Abbas:
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ ، قَالَ حَدَّثَنَا هَاشِمُ بْنُ الْقَاسِمِ ، قَالَ حَدَّثَنَا وَرْقَاءُ ، عَنْ عُبَيْدِ اللَّهِ بْنِ أَبِي يَزِيدَ ، عَنِ ابْنِ عَبَّاسٍ ، أَنَّ النَّبِيَّ صلى الله عليه وسلم دَخَلَ الْخَلاَءَ، فَوَضَعْتُ لَهُ وَضُوءًا قَالَ " مَنْ وَضَعَ هَذَا ". فَأُخْبِرَ فَقَالَ " اللَّهُمَّ فَقِّهْهُ فِي الدِّينِ " .
Once the Prophet (ﷺ) entered a lavatory and I placed water for his ablution. He asked, "Who placed it?" He was informed accordingly and so he said, "O Allah! Make him (Ibn `Abbas) a learned scholar in religion (Islam).