Ubayy bin Ka'b reported that the Apostle of Allah (ﷺ) was near the tank of Banu Ghifar that Gabriel (ؑ) came to him and said: Allah has commanded you to recite to your people the Qur'an in one dialect. Upon this he said: I ask from Allah pardon and forgiveness. My people are not capable of doing it. He then came for the second time and said: Allah has commanded you that you should recite the Qur'an to your people in two dialects. Upon this he (the Holy prophet) again said: I seek pardon and forgiveness from Allah, my people would not be able to do so. He ( Gabriel (ؑ)) came for the third time and said: Allah has commanded you to recite the Qur'an to your people in three dialects. Upon this he said: I ask pardon and forgiveness from Allah. My people would not be able to do it. He then came to him for the fourth time and said: Allah has commanded you to recite the Qur'an to your people in seven dialects, and in whichever dialect they would recite, they would be right.
Hadith Referenceصحيح مسلم / کتاب فضائل القرآن وما يتعلق به / 821
´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.'"
Hafiz Muhammad Ameen
942. Commentary: Whenever there is a difference of opinion regarding any issue, one should refer back to Allah and His Messenger, that is, seek guidance from the Qur’an and Sunnah; one should not rely on personal reasoning (ijtihad) and conjectures.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 942
Ubayy bin Kab reported: The Prophet ﷺ said: "Ubayy, I was asked to recite the Quran and I was asked: 'In one mode or two modes?' The angel that accompanied me said: 'Say, in two modes', I said: 'In two modes', I was asked again: 'In two or three modes'. The matter reached up to seven modes. He then said: 'Each mode is sufficiently health-giving, whether you utter 'all-hearing and all-knowing' or instead 'all-powerful and all-wise'. This is valid until you finish the verse indicating punishment on mercy and finish the verse indicating mercy on punishment. "
Shaykh Umar Farooq Saeedi
1477. Commentary: This narration is authentic according to Shaykh al-Albani rahimahullah. However, in the latter verses, the concession to alter the Divine Attributes was granted only to the Messenger of Allah sallallahu alayhi wa sallam. No one from the Ummah has this right. It is obligatory to adhere to the established and mutawatir (mass-transmitted) recitation proven from the Messenger of Allah sallallahu alayhi wa sallam.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 1477