Chapter 1: The Book of Purification
It was narrated from Anas that a Bedouin urinated in the Masjid, and some of the people went after him, but the Messenger of Allah (ﷺ) said: "Leave him and do not restrain him." When he had finished he called for a bucket (of water) and poured it over it. [1]
Abu 'Abdur-Rahman (An-Nasa' i) said: "Meaning: 'Do not interrupt him.'"
[1] The author will cite this narration again in No. 330 as a possible proof for setting the minimum, since it mentions "a bucket" as if this is the minium amount required.
Sunan an-Nasa'i 53