Musnad Ahmad 5:455

'Abd al-Rahman narrated to us, from Sufyan, and 'Abd al-Razzaq, Sufyan informed us, from 'Asim—meaning Ibn Kulayb—from Abu Burdah, from 'Ali, who said: "The Messenger of Allah (ﷺ) forbade me from placing the ring on this one or this one." 'Abd al-Razzaq said: "Meaning his two fingers: the index finger and the middle finger."