Islaam has forbidden the calls of jaahiliyyah (the prelslaamic days of ignorance) and there are many textual evidences which forbid all of the characteristics and manners of jaahiliyyah and their actions, except those (good and decent) practices which Islaam agreed to. And there is no doubt that the call to nationalism is from these calls of jaahiliyyah, since nationalism is a call to other than Islaam and an aiding of other than the truth. And how many ills, evils and serious wars has such calls of jaahi liyyah caused to their people, causing great harm to their souls, their wealth and their possessions. The consequences of such calls (for the Muslims) was a splitting up of their unity and a planting of enmity and hatred of each other in their hearts and a fragmentation and splitting between tribes and nations.
Ibn Taymiyyah (d.728H) rahimahullaah said:  "Everything which is outside the call of Islaam and the Qur'aan, with regards to lineage, land, nationality, schools of thoughts and ways, then it is from the calls of jaahiliyyah. lndeed, even when the Muhaa jirs (those Companions who migrated from Makkah to Madeenah) and the Ansaars (those Companions who aided and supported those who migrated) argued, such that one of the Muhaajirs said:" O Muhaajirs! (implying; rally to my aid) " And one of the Ansaar said: "O Ansaar!" Upon hearing this, the Prophet sallallaahu 'alayhi wa sallam said: "Is it with the calls of Jaahiliyyah that you call, and l am still amongst you!" And he became very angry at that."
And from the textual evidences pertaining to this issue is Allaah the Most High's
"And stay in your homes and do not display yourselves, like the display of the times of jaahiliyyah (pre lslaamic ignorance). But establish the Prayer, give the Zakaat and obey Allaah and His Messenger." [Soorah alAhzaab 33:33]
"When those who disbelieved placed in their hearts pride and arrogance the pride and arrogance of jaahiliyyah then Allaah sent down His tranquillity upon His Messenger sallallaahu 'alayhi wa sallam and upon the Believers ..." [Soorah alFath 48 26].
The Prophet sallallaahu 'alayhi wa sallam said: "Whosoever leaves off obedience and separates from the Jamaa'ah and dies, he dies a death of jaahiliyyah. Whoever fights under the banner of the blind, becoming angry for 'asabiyyah (partisanship and party spirit), or calling to 'asabiyyah, or assisting 'asabiyyah, then dies, he dies a death of jaahiliyyah." 
Also in Saheeh Muslim (8/120) the Prophet sallallaahu 'alayhi wa sallam said: lndeed Allaah has revealed to me that you should have humility, and that no one should act proudly and oppressively over anyone else, nor should anyone boast over anyone else. "
And there is no doubt that the call to nationalism is a call to 'asabiyyah (partisanship and party spirit) and it is a call to becoming angry for the sake of 'asabiyyah and fighting for 'asabiyyah. And there is no doubt also, that the call to nationalism is a call to transgression, pride and arrogance, since nationalism is not a divinely revealed way of life which prevents its people from oppression and proud boasting. Rather it is an ideology from the time of jaahiliyyah which leads its people to boastin g about it and having 'asabiyyah for it even if they are the oppressors and the others are the oppressed ! So O noble reader consider this and the truth will be clear to you.
And from the textual evidences connected with this is what at-Tirmidhee relates from Allaah's Messenger sallallaahu 'alayhi wa sallam that he said: "Let people stop boasting about their forefathers who have died, who are merely fuel for the Hell Fire; or they will certainly be more insignificant with Allaah than the beetle which roles dung with its nose. Allaah has removed from you the party spirit of the days of jaahiliyyah and the boasting about one's forefathers. Indeed a person is either a pious Belie ver or a wretched sinner. All of mankind are the children of Aadaam, and Aadam was created from clay.
The Prophet sallallaahu 'alayhi wa sallam also said: "Indeed there is no excellence for an arab over a non-arab, nor a non-arab over an arab, nor a white person over a black one, nor a black person over a white one, except through taqwaa (piety and obedie nce to Allaah) 
And this accords with Allaah the Most High's saying:
"O mankind! We have created you from male and female and have made you into nations and tribes, that you may know one another. Indeed the most noblest of you with Allaah is the one who has the most taqwaa." [Soorah al-Hujuraat 49:13].
So Allaah the One free from all defects- made clear in this noble aayah (verse) that people have been made into nations and tribes so that they may come to know each other, not that they should boast and have pride over one another. And Allaah the Most Hi gh considered the most noblest of them to be the one with the most piety and taqwaa. Likewise, the previously mentioned narration shows the same meaning, and guides to the fact that it is from the ways of jaahiliyyah to vainly boast and to have false prid e for one's fore fathers and ancestry. This is what the calls of jaahiliyyah lead to, whereas Islaam is in opposition to this. Rather Islaam calls to modesty, humility, taqwaa and to having love for the sake of Allaah, and that the true and sincere Muslims are merely one of the categories of the children of Aadam 'alayhis salaam, and that the Muslims are a single body and a single structure; each part supporting the other and each part feeling the pain that the other parts are suffering as occurs in an a uth entic hadeeth (narration) from the Prophet sallallaahu 'alayhi wa sallam, that he said: "The Believer to the Believer is like a solid building, one part supports the other." And he interlaced his fingers to demonstrate this.
The Prophet sallallaahu 'alayhi wa sallam also said: "The example of the Believer in their mutual love and mercy is like the example of a body, if one part of the body feels pain, then all the body suffers in sleeplessness and fever. 
O people! I call to you in the name of Allaah. Does your nationalism call you to these noble manners of mercy and kindness to the Muslims the arabs and the non arabs and of having mutual sympathy and concern for them, and feeling pain at their pain? No by Allaah! Rather it calls you to having allegiance with those who have evil character and it calls you to cultivating enmity and hatred for those who deny this false creed of nationalism . So beware, O Muslim who desires safety and salvation, and consider the reality of the affair with a fair consideration, without being prejudiced with party spirit and desires. Only then you will see the reality as it truly is. So may Allaah guide me and you to the means of safety and salvation.
And it is related by Imaam al-Bukhaaree in his Saheeh (8/137), that a young man from the Muhaajirs and a young man from the Ansaar quarreled. So the Muhaajir said: "O Muhaajirs! (meaning: rally to my help)" And the Ansaaree said: "O Ansaar'" So the Prophet sallallaahu 'alayhi wa sallam heard this and said: ''Is it with the call off jaahiliyyah that you are calling out, and I am present amongst you !"
Even though the term Muhaajir and Ansaar are two ascriptions which are beloved to
Allaah the One free from all defects and He has praised these two groups with a very great
praise, in His the Most High's saying:
"And the first to embrace Islaam from the Muhaajirs and the Ansaar, and those who followed them in goodness, beliefs and actions. Allaah is well pleased with them, and they are well pleased with Him. He has prepared for them Gardens of Paradise, beneath w hich rivers flow, to live therein forever. That is the supreme achievement." [Soorah at-Tawbah 9:100].
Yet in the above incident, this ascription to the Muhaajirs and seeking the help from them, and the Ansaar and seeking the help from them, when the likes of this was considered to be from the calls of jaahiliyyah, then what about those who claim allegianc e to nationalism and seek help through that and become angry for that? Will this not be more fitting to be considered one of the calls from the days of jaahiliyyah? This is a matter in which there is no doubt, and it is one of the clearest of all matters.
And this is what has been established in the authentic hadeeth (narration), from alHaarith alAsh'aree radiallaahu 'anhu, that the Prophet sallallaahu 'alayhi wa sallam said: "I order you with five things which Allaah ordered me with: The Jamaa'ah, hearing , obeying, hijrah (migration) and jihaad in the way of Allaah the Mighty and Majestic. So whosoever separates from the Jamaaah by a handspan, throws the yoke of Islaam from his neck, unless he repents. And whosoever calls with the call of jaahiliyyah (the days of ignorance), then he is from the hoarded heap of Hell Fire" It was said: Even if he fasts and prays? He said: "Even if he fasts and prays. So call with the call of Allaah which Allaah gave: The Muslims, the Believers, Worshippers of Allaah.' 
This hadeeth is absolutely clear with regards to rendering futile the calls to nationalism. Its callers deserve that they should be from the heap of Hell Fire, even if they fast and they Pray and claim that they are Muslims. So what a severe threat and se vere warning is given here; warning every muslim from the calls of jaahiliyyah and warning them from entering into this even if such calls are adorned with false talks and enchanting speeches . Rather it is a deception and a blind following which leads it s people to the worst and most despicable of ends. And we ask Allaah for safety and freedom from that.
1. Nuqdul-Qawniyyatul Arabiyyah (pp.39-44), slightly edited.
2. Majmoo ul-Fataawaa (3/456).
3. Related by al-Bukhaaree (8/137).
4. Related by Muslim in his Saheeh (6/21), from Abu Hurayrah radiallaahu anhu.
5. Hasan: Related by Abu Daawood (no.5116) and at-Tirmidhee (no.4233) from Abu Hurayrah radiallaabu anhu.
It was authenticated by Ibn Taymiyyah in Kitaabul-lqtidaa (p.35).
6. Saheeh: Related by Ahmad (5/411) and it was authenticated by Ibn Taymiyyah in Kitaabul-lqtidaa (p.69).
7. Related by al-Bukhaaree (no.481) and Muslim (no.2585) from Abu Hurayrah radiallaabu anhu.
8. Related by al-Bukhaaree (no.6011) and Muslim (no.2586) from an-Nu'maan ibn Basheer radiallaahu anhu.
9. Saheeh: Related by at-Tirmidhee (nos.2863) and at-Tilyaalasee (no.1161) and others. It was authenticated by Shaykh al-Albaanee in his checking to Ibn Abee 'Aasim's as-Sunnah
Nationalism can be defined as a bond between people of the same race who are proud of their race and work to dominate others, because it is an extension of the overpowering tendencies in individuals towards other people. This feeling comes into being when the thinking of a person is very shallow.
By examining the history, one would clearly realize that the most evident cause for the destruction of the Khilafah was nationalism. The colonial forces have established it in the Muslims' lands to move the Muslims away from Islam in order to tear up their unity, destroy their state, to implement the ideas of kufr, hence to prevent the return of implementing the rules of Islam and the Khilafah to earth. In the Quran, Allah says, "Hold fast to the rope of Allah and be not divided amongst yourselves." Yet, the Muslims ignore this injunction of Allah (swt).
Nationalism is not compatible with the principles and justice of Islam at all; because it calls for the protection and help of one's own race even at the cost of destroying others. Islam does not recognize borders or racial barriers. The Khalifah al-Muatasim beautifully demonstrated this Islamic concept. He was able to spread the mercy and justice of the ideology of Islam to the whole world. That Ummah was feared by all, for it would rush to help if any part of it was threatened, even if it was a single Muslim woman.
However, when the Muslim Ummah started thinking from a different point of view, other than that of Islam, it was defeated. First, its divine laws were abolished by the destruction of the Khilafah State, then it was divided and fragmented to small parts and were made "independent states" headed by agents of the kuffar.
The loyalty of the Muslims shifted from Islam to these artificial "states" because their allegiance was not to Islam but to nationalism. The result of this attitude is apparent. Since then, Islam continues to be under physical and intellectual attack. The rapes, killings, starvation, humiliation, and more importantly the implementation of kufr are well spread all over the Muslim world. The only way the Ummah can revive is by putting Islam alone as the basis for its thinking.
So my dear brothers and sisters in Islam, we must act now to demolish all these "non-Islamic nationalistic independent states," that are keeping us disunited and away from Islam. Only then will we act as one strong Ummah united by holding fast to the rope of Allah. We must, as ordered by Allah, work relentlessly to establish this Islamic State that will unite all Muslims under one flag, that of La-illahha-illalla, Muhammad-ur-Rasul-Allah.