Sunan Ibn Majah 351
سنن ابن ماجه#351Da'ifIt was narrated that Abu Hurairah said:"A man passed by the Prophet while he was urinating, and greeted him with the Salam, but he did not return the greeting. While he finished, he struck the ground with his palms and did dry ablution (Tayammum), then he returned the greeting
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautVery Daif
Zubair Ali ZaiDaif
In-book reference: 1:85