Musannaf Ibn Abi Shayba 3:196

Abu Bakr narrated to us, Waki’ narrated to us, from Sufyan, from ‘Asim, from Abu al-Duha, who said: ‘Ali used to say in his bowing (ruku’): "Glory be to my Lord, the Magnificent" (Subhana Rabbi al-‘Azim) three times. And in his prostration (sujud): "Glory be to my Lord, the Most High" (Subhana Rabbi al-A’la) three times.