Sahih al-Bukhari 154
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · While passing urine one should not hold his penis with his right hand.
Narrated Abu Qatada:
حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ ، قَالَ حَدَّثَنَا الأَوْزَاعِيُّ ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي قَتَادَةَ ، عَنْ أَبِيهِ ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِذَا بَالَ أَحَدُكُمْ فَلاَ يَأْخُذَنَّ ذَكَرَهُ بِيَمِينِهِ، وَلاَ يَسْتَنْجِي بِيَمِينِهِ، وَلاَ يَتَنَفَّسْ فِي الإِنَاءِ " .
The Prophet (ﷺ) said, "Whenever anyone of you makes water he should not hold his penis or clean his private parts with his right hand. (And while drinking) one should not breathe in the drinking utensil ."