Sahih Muslim Book 4, Hadith Number 870.

Chapter : The command to observe prayer with tranquillity and calmness and forbiddance of making gesture with hands and lifting them while pronouncing salutation, and the completing of first rows and joining together well in them.

Abdullah b. Mas’ud reported: The Messenger of Allah (may peace be upon him) said: Let those who are sedate and prudent be near me, then those who are next to them (saying it three times), and beware of the tumult of the markets.