(18) باب النَّهْىِ عَنْ الاِسْتِنْجَاءِ، بِالْيَمِينِ
Narrated Abu Qatada:
Allah's Messenger (ﷺ) said, "Whenever anyone of you drinks water, he should not breathe in the drinking utensil, and whenever anyone of you goes to a lavatory, he should neither touch his penis nor clean his private parts with his right hand."
Reference: Sahih al-Bukhari 153
In-book reference: Book 4, Hadith 19
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 4, Hadith 155