Musnad Abu Ya'la al-Mawsili 3:276

Abu Hisham al-Rifa'i narrated to us, Abu Bakr ibn 'Ayyash narrated to us, from 'Asim, from Zirr, from 'Abdullah, who said: I said to a man, "Recite to me thirty verses from [Surah] al-Ahqaf," and he recited to me differently than how the Messenger of Allah (ﷺ) had recited to me. I said to another, "Recite to me thirty verses from [Surah] al-Ahqaf," and he recited to me differently than how the first one had recited to me. So I came to the Messenger of Allah (ﷺ), and 'Ali was sitting with him. 'Ali said, "The Messenger of Allah (ﷺ) says: 'Recite as you have been taught.'"