"O you who believe! Fear Allah as He should be feared and die not except in a state of Islam with complete submission to Allah. And hold fast, all of you together, to the rope of Allah (i.e. Qur'an), and be not divided among yourselves; and remember with gratitude Allah's favors on you; for you were enemies and He joined your hearts in love, so that by His Grace you became brothers; and you were on the brink of the pit of fire, and He saved you from it. Thus Allah make His signs clear to you that you may be guided."[Surah Al'Imran (3); ayah 102-103]
It is narrated by Qatada that Ibnu Abi Hathim said that in the verses quoted above Allah (swt) has ordered the Muslims to hold fast to the book of Allah, His Deen, and to his covenant, and He has forbidden the Muslims to divide amongst themselves and to dispute with each other.
In another incident, Jabir ibn `Abd Allah al Ansari, narrated what happened at the watering place of al Muraysi which led to the Munafiqun stirring up the traces of `Asabiyyah and seeking to destroy the unity of the Muslims. He said:
"We were on a raid when one of the Muhajirun kicked one of the Ansar. The Ansar said, `O Ansar! Help me! (calling his tribe) and the Muhajir said, `O Muhajirun! Help me! (calling his tribe). The Messenger of Allah (saaw) heard them and said, "Why are you stirring up something which belongs to Jahilliyah?"