The Quran condemns all sects. All sects in Islam, whether Sunni, Shias, Ahmaddis, Wahabbi’s have disagreements about hadith/sunnah attributed to the prophet. However, these same sects have no disagreements about the Quran.
It is sources of religious law, stories, conjecture, etc. outside the Quran which have created these sects. At the end of this article three “authentic” hadith have been produced about the last sermon of the prophet. The different versions/conjecture gave rise to sects.
The followers of Nation of Islam claim to be Muslim but they follow sources outside the Quran for their religious laws. The other sects of Islam ( Sunni, Shias, Ahmaddis, etc.) do exactly the same thing – they follow sources and religious scholars, instead of the Quran.
[6:159] Those who divide themselves into sects do not belong with you. Their judgment rests with GOD, then He will inform them of everything they had done.
[30:32] (Do not fall in idol worship,) like those who divide their religion into sects; each party rejoicing with what they have.
[42:14] Ironically, they broke up into sects only after the knowledge had come to them, due to jealousy and resentment among themselves. If it were not for a predetermined decision from your Lord to respite them for a definite interim, they would have been judged immediately. Indeed, the later generations who inherited the scripture are full of doubts.
The last sermon of the prophet witnessed by the thousands has three versions. The versions the references are listed below.
1) I leave with you Quran and Sunnah. Muwatta, 46/3
2) I leave with you Quran and Ahl al-bayt. Muslim 44/4, Nu2408; ibn hanbal 4/366; darimi 23/1, nu 3319.
3) I leave you for the Quran alone you shall uphold it. Muslim 15/19, nu 1218; ibn Majah 25/84, Abu dawud 11/56.
Because the majority of the Muslims follow conjecture (hadith and sunnah) instead of Quran alone (17:46) as our Creator has commanded the “Muslims” are divided into sects. These sects are there because of differences and disagreements on Hadith rather than disagreements over the Quran.
Some Muslims also use surah 37 verse 83 to back up the idea that it is ok to belong to a sect. The verse reads:
[37:83] Verily among those who followed his Way was Abraham
(shi’a) in Arabic has many meanings depending on the context. It’s root is meaning “group”. In the first verse we have to look at the preceding verse.
So from Surah 37:75-83 we can clearly tell that Allah was speaking of Noah first, and then describing Abraham as being part of his group. In this context it means that he was his descendant (genetically or spiritually). It does not mean sect (as in a religious group among many).
Now in this verse it is explicit what kind of “group” Allah is referring to:
Surah 6:159 – Indeed, those who have divided their religion and become sects – you, [O Muhammad], are not [associated] with them in anything. Their affair is only [left] to Allah; then He will inform them about what they used to do.
Here we are dealing with religious groups that have splintered, i.e. sects. And it is clear from the tone of verse that this is not a good thing.