Sahih Muslim: Book 5, Hadith 31

Al-Aswad and ‘Alqama reported: We came to the house of ‘Abdullah b. Mas’ud. He said: Have these people said prayer behind you? We said: No. He said: Then stand up and say prayer. He neither ordered us to say Adhan nor Iqama. We went to stand behind him. He caught hold of our hands and mode one of us stand on his right hand and the other on his left side. When we bowed, we placed our hands on our knees. He struck our hands and put his hands together, palm to palm, then put them between his thighs. When he completed the prayer he said. There would soon come your Amirs, who would defer prayers from their appointed time and would make such delay that a little time is left before sunset. So when you see them doing so, say prayer at its appointed time and then say prayer along with them as (Nafl), and when you are three, pray together (standing in one row), and when you are more than three, appoint one amongst you as your Imam. And when any one of you bows he must place his hands upon hie thighs and kneel down. and putting his palms together place (them within his thighs). I perceive as if I am seeing the gap between the fingers of the Messenger of Allah (may peace he upon him).