The Messenger of Allah ﷺ said, "When one of you drinks, he should not breathe into the vessel. When one of you urinates, he should not hold his private parts with his right hand. And when one of you cleans himself, he should not clean himself with his right hand."
قال رسول الله ﷺ: إذا شرب أحدكم فلا يتنفس في الإناء، وإذا بال أحدكم فلا يمسح ذكره بيمينه، وإذا تمسح أحدكم فلا يتمسح بيمينه.
Bukhari narrated it in the Book of Drinks (5630), and Muslim in the Book of Drinks (267:63), both of them via Yahya bin Abu Kathir, from Abdullah bin Abu Qatada, from his father, who mentioned it.