Islamic civilization in its early days detected identity barriers with disbelievers as outsiders. Meanwhile, it showed tolerant and moderate attitude toward them. This factor led to spiritual extension and Islam durability among the residents of the Islamic newly conquered regions. But as Islamic civilization grew weak, getting away from original Islam and facing with external and aggressive otherness like Moguls, Crusaders and also dominance of Turks Caliphate System, extension of classes

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... d from Islam and xenophobic attitude among Takfiri group become widespread. This approach targeted outsiders from the beginning and represented the strictest treatment to them; but through time by with diversification of the derivations in Islamic world, Takfirist grew hostile toward other Islamic sects. In this paper we try to explain background of otherness and excommunication in the Islam world. It is elucidated that at the beginning the range of atheism and other definition was so narrow and restricted to Combat Unbelievers, but along with development of Salafi thoughts and using external factors, not only it was extended but it was turned into a tool for eliminating rival identities.