Sahih Bukhari Volume 1, Book 11, Hadith Number 695

Narated By Ibn ‘Abbas : One night I stood to the left of the Prophet in the prayer but he caught hold of me by the hand or by the shoulder (arm) till he made me stand on his right and beckoned with his hand (for me) to go from behind (him). (Al-Kashmaihani-Fateh al-Bari).