´Suhaib narrated:` "I passed by Allah's Messenger (S) while he was performing Salat, so I said greeted him with Salam, and he returned it by making signals." He said: "I do not know except that he said: 'He indicated with his finger.'"
Hadith ReferenceSunan at-Tirmidhi / The Book on Salat (Prayer) / Hadith: 367