(6) باب رَدِّ السَّلاَمِ بِالإِشَارَةِ فِي الصَّلاَةِ
It was narrated that Suhaib, the Companion of the Messenger of Allah (ﷺ) said:
"I passed by the Messenger of Allah (ﷺ) when he was praying, and greeted him with Salam. He returned my greeting with a gesture, or maybe it was just with his finger."
Reference: Sunan an-Nasa'i 1186
In-book reference: Book 13, Hadith 8
English translation: Vol. 2, Book 13, Hadith 1187