"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."
Sunan an-Nasa'i Book 13, Hadith 8
← Previous Hadith "We used to pray behind the Messenger of Allah (ﷺ) and we would greet (others) with our hands. He said: 'What is the matter with those who greet (others) with their hands as if they were tails of wild horses? It is sufficient for any one of you to put his hand on his thigh and say: "As-salamu 'alaikum, as-salamu 'alaikum."

Sunan an-Nasa'i Book 13, Hadith 7 Next Hadith → "Ibn 'Umar said: The Prophet (ﷺ) entered the Masjid of Quba' to pray there, then some men came in and greeted him with Salam. I asked Suhaib, who was with him: 'What did the Messenger of Allah (ﷺ) do when he was greeted?' He said: 'He used to gesture with his hand.'"

Sunan an-Nasa'i Book 13, Hadith 9