It wasnarrated that Jabir said:
"The Prophet (ﷺ) sent me on anerrand,then I caught up with him while he was performing prayer, andIgreeted him. He gestured to me, then when he finished, he called meand said: 'You greeted me before, but I was performing prayer.'" (FR)
English reference (FR): Vol. 1, Book 5, Hadith 1018 (FR)
Arabic reference (FR): Book 5, Hadith 1071 (FR)