Indeed, Islam has forbidden the calls of the Days of Ignorance (jahiliyyah). There are many text evidences that forbid all of the characteristics and deeds of these times of Ignorance, except for those (good) practices, which Islam has condoned. And from that which there is no doubt of, is that the call to NATIONALISM is indeed one of these calls of Jahiliyyah. This is because nationalism is a call to something other than Islam and a support for something other than the truth. And how many crimes, evils and severe wars has such calls of Jahiliyyah brought about upon the people, causing great harm to their souls, their wealth and their possessions. The consequences of such calls was a break in their (Muslim) unity, a harvesting of Enmity and Hatred for one another, in their hearts, and a splitting between them into tribes and nations!
Ibn Taimiyyah (ra) said: “Everything that is foreign to the call of Islam and the Quran, with regards to lineage, land, nationality, schools of thoughts and methodologies, then that is from the calls of the Days of Ignorance (jahiliyyah). Once the Muhajireen and the Ansaar argued, such that one of the Muhajireen said:’O Muhajireen!’ (meaning, come to assist me) And one of the Ansaar said: ‘O Ansaar!’ Upon hearing this, the Prophet (PBUH) said: ‘Is it with the calls of Jahiliyyah that you cry out, while l am still amongst you?!’ Al-Bukhari (8/137) And he became very angry at that.”
From the text evidences concerning this issue, is Allah the Most High’s saying: “When those who disbelieved placed in their hearts, pride and arrogance – the pride and arrogance of the Times of Ignorance (Jahiliyyah), then Allah sent down His tranquillity upon His Messenger and upon the believers. ” Surat-ul-Fath (48):26
The Prophet (PBUH) said: “Whosoever leaves off obedience and separates from the Jamaa'ah and then dies, he dies a death of (one in) the Days of Ignorance (Jahiliyyah). Whosoever fights under the banner of the blind, becoming angry for partisanship (asabiyyah), calling towards it, or supporting it and then dies, he dies a death of (one in) the Days of Ignorance (Jahiliyyah).” Muslim in his Saheeh (6/21)