(6) باب رَدِّ السَّلاَمِ بِالإِشَارَةِ فِي الصَّلاَةِ
It was narrated that Jabir said:
"The Messenger of Allah (ﷺ) sent me on an errand then I came back to him while he was praying. I greeted him with the salam and he gestured to me. When he finished he called me and said: 'You greeted me with Salam just now and I was praying.' And he was facing toward the east that day."
Reference: Sunan an-Nasa'i 1189
In-book reference: Book 13, Hadith 11
English translation: Vol. 2, Book 13, Hadith 1190