Musannaf Ibn Abi Shayba 3:147

Abu Bakr narrated to us, he said: Al-Ahwas narrated to us, from ‘Ata’ ibn al-Sa’ib, from Salim ibn al-Bara’, he said: We came to Abu Mas’ud and said: "Show us the prayer of the Prophet, may Allah bless him and grant him peace." So he said "Allahu Akbar" (takbir), then he bowed and placed his hands upon his knees, then he said: "Thus he prayed with us."