Nationalism is a concept alien to Islam because it calls for unity based on family and tribalistic ties, whereas Islam binds people together on the Aqeedah and Emaan. That is, belief in Allah (swt) and His Messenger (saws).
Therefore grouping together on tribalistic lines is clearly forbidden. It is narrated by Abu Dawud that the Messenger of Allah (saws) said, "
He is not one of us who calls for 'asabiyyah, (nationalism) or who fights for 'asabiyyah or who dies for 'asabiyyah." And in another hadith, the Messenger of Allah (saws) referring to nationalism, racism, and patriotism said "
Leave it, it is rotten". [Muslim and Bukhari]
The messenger of Allah (saws) had rebuked those who upheld nationalism. On one occasion a party of Jews conspired to bring about disunity in the ranks of the Muslims after seeing the Aus and Khazraj within Islam. A youth from amongst them was sent to incite remembrance of the battle of Bu'ath where the Aus had been victorious over the Khazraj, and he recited poetry to bring about division between them. As a result there was a call to arms. When the news reached the Messenger of Allah (saws), He (saws) said, "
O Muslims, remember Allah, remember Allah. Will you act as pagans while I am present with you after Allah has guided you to Islam, and honoured you thereby and made a clean break with paganism; delivered you thereby from disbelief; made you friends thereby?" When they heard this they wept, and embraced each other. This incident clearly highlights how the messenger of Allah (saws) rebuked any forms of tribalism and nationalism. Allah (swt) then revealed the verses,
"O you who believe! Fear Allah as He should be feared and die not except in a state of Islam. And hold fast together all of you to the rope of Allah, and be not divided among yourselves; and remember with gratitude Allah's favours 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 makes His signs clear to you that you may be guided." [Qur'an 3: 102-103]
The incidents above demonstrate that tribal ties have no place in Islam. Muslims are commanded to stick together and not to disassociate themselves from each other just because they comes from different tribes or backgrounds.
The Messenger of Allah (saws) also said, "
The Muslims are like a body, if one part of the body hurts, rest of the body will also suffer" [Muslim] meaning that the Muslims, whether they are of Chinese, African, or Arabian or European origin, are one Ummah and they cannot be separated from each other. Furthermore, Allah (swt) says: "
The faithful are but brothers..." [Qur'an 49: 10] . No nationalistic ties should ever break their unity. That is the beauty of Islam.
Now the speech of Allah (swt) addressed to the Messenger (saws) is also a speech to his Ummah, unless specific evidence comes to restrict this. In this case, there is no such restriction, so it becomes obligatory for the Muslims to rule according to Islamic teachings. And ruling according to Islam leaves no room for nationalistic constitutions whatsoever because what is applied (and what forms the criteria for judgement) is the Book of Allah (swt) and the Sunnah of the Messenger (saws). Allah (swt) says,
"It is not for a believer (male or female) that when Allah and His Messenger have decided a matter that they should have any choice in the matter." [Qur'an 33: 36]
Hence since Islam has prohibited nationalism, it becomes a duty of every Muslim, in the present situation, to work towards tearing down the nationalistic boundaries that are artificially created in Muslim lands, and to remove any obstacles which allow its propagation. And those who still uphold nationalism, remember what Allah (swt) says, "
Those who oppose Allah's order have to be warned that a calamity may strike them or a painful doom may fall upon them." [Qur'an 24: 63]
I ask Allah (swt) to guide us all and make our hearts pure..
http://www.missionislam.com/knowledge/Nationalism.htm