"Bring me (water for) Wudu'." So I brought him (water for) Wudu', and he performed Wudu' and wiped over his Khuffs. The Shaikh said: "Isma'il (one of the narrators) is Ibn Ja'far bin Abi Kathir Al-Qari.

Meaning the author, and it appears that Ibn As-Sunni who heard the text, said this.
Sunan an-Nasa'i Book 1, Hadith 17
← Previous Hadith "I went out with the Messenger of Allah (ﷺ) to an isolated area, and when he wanted to relieve himself he moved far away."

Sunan an-Nasa'i Book 1, Hadith 16 Next Hadith → "I was walking with the Messenger of Allah (ﷺ) and he came to some people's garbage dump and urinated while standing up. I turned to go away, but he called me back (to conceal him), and I was just behind him. Then when he had finished, he performed Wudu' and wiped over his Khuffs."

Sunan an-Nasa'i Book 1, Hadith 18