´It was narrated that Ibn 'Umar said:` "A man passed by the Prophet (ﷺ) when he was urinating and greeted him with Salam, but he did not return his greeting."
Hadith Referenceسنن نسائي / ذكر الفطرة / 37
Hadith Gradingالألبانی:حسن صحيح | زبیر علی زئی:صحيح مسلم