"I asked the Messenger of Allah about looking around during the Salat. He said: 'It is a portion which the Shaitan snatches during a man's prayer.'"
Jami` at-Tirmidhi Book 6, Hadith 47
← Previous Hadith "The Messenger of Allah said to me: 'O my son! Beware of looking around during the Salat, for indeed looking around during Salat is destruction. If you must do so, then in the voluntary (prayers), not in the obligatory (prayers).'" (Da'if)

Jami` at-Tirmidhi Book 6, Hadith 46 Next Hadith → the Messenger of Allah said: "When one of you comes to the Salat and (finds) the Imam is in a position, then do as the Imam is doing."

Jami` at-Tirmidhi Book 6, Hadith 48