Musnad Ahmad 3883

It was narrated that 'Abdullah (رضي الله عنه) said: I heard a man reciting a verse differently than the way the Messenger of Allah (ﷺ) taught it to me, so I took him by the hand and brought him to the Messenger of Allah (ﷺ), who said: “Both of you have done well.” And he got so angry that anger could be seen in his face. Shu'bah said: I think it most likely that he said: “Do not differ, for those who came before you differed concerning it, then they were doomed.”