Musannaf Ibn Abi Shayba 3:6345

Waki’ narrated to us, he said: ‘Abd al-Salam ibn Shaddad Abu Talut al-Jariri narrated to us, from Ghazwan ibn Jarir al-Dabbi, from his father, who said: When ‘Ali stood in prayer, he would place his right hand upon his wrist. He would remain like that until he bowed, whenever he bowed, unless he was adjusting his garment or scratching his body.