سنن النسائي

It was narrated that Ubayy said: "I had no confusion in my mind from that time I embraced Islam, except when I recited a verse and another man recited it differently. I said: 'The Messenger of Allah (ﷺ) taught me this.' And the other man said: 'The Messenger of Allah (ﷺ) taught me too.' So I went to the Prophet (ﷺ) and said: 'O Prophet of Allah, did you not teach me such and such a verse?' He said: 'Yes.' The other man said: 'Did you not teach me such and such a verse?' He said: 'Yes. Jibril and Mika'il, peace be upon them, came to me, and Jibril sat on my right and Mika'il on my left. Jibril, peace be upon him, said: "Recite the Quran with one way of recitation.' Mika'il said: 'Teach him more, teach him more- until there were seven modes of recitation, each of which is good and sound.'"