´It was narrated that Ubayy bin Ka'b said:` "The Messenger of Allah (ﷺ) taught me a surah, and when I was sitting in the masjid I heard a man reciting it in a way that was different from mine. I said to him: 'Who taught you this surah?' He said: 'The Messenger of Allah (ﷺ).' I said: 'Stay with me until we go to the Messenger of Allah (ﷺ).' So we came to him and I said: 'O Messenger of Allah, this man recites a surah that you taught me differently.' The Messenger of Allah (ﷺ) said: 'Recite, O Ubayy.' So I recited it, and the Messenger of Allah (ﷺ) said to me: 'You have done well.' Then he said to the man: 'Recite.' So he recited it and it was different to my recitation. The Messenger of Allah (ﷺ) said to him: 'You have done well.' Then the Messenger of Allah (ﷺ) said: 'O Ubayy, the Quran has been revealed with seven different modes of reciation, all of which are good and sound."
Hadith Referenceسنن نسائي / كتاب الافتتاح / 941
Hadith Gradingالألبانی:حسن صحيح | زبیر علی زئی:إسناده حسن
1؎: The author has used the word «القوی» with the definite article "al-", by which, according to the Imams of al-Jarh wa al-Ta'dil, it is meant that "they are not as strong as a narrator of sahih (authentic) hadith ought to be." According to Hafiz Ibn Hajar, they are «صدوق یخطیٔ», that is, they are trustworthy (thiqah) in terms of integrity, but their memory is somewhat weak. When supported by corroborating narrations (mutaba'at) and witnesses (shawahid), their narration attains the level of hasan sahih.
´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