The Holy Prophet of Islam (peace be upon him and his progeny) said:
لا يَبْقَى عَلَى ظَهْرِ الأَرْضِ بَيْتُ مَدَر وَ لا وَبَر إلاّ أَدْخَلَهُ اللّهُ كَلِمَةَ الإِسْلامِ
There will not remain any house on the earth, not even mud houses and woollen tents, that will not be filled by Allah with the religion of Islam
Everyday this reality becomes more obvious , i.e., that the world has two alternatives: either it will accept Islam, or it will not accept any religion. And since being without a religion is against man’s nature, it shall finally accept Islam. At present a wave of attention to Islam has permeated different parts of the world.
But this matter would be accomplished upon the advent of Imam Mahdi (may our soul be sacrificed for him). Thereupon, idolatry and polytheism would be removed from the earth and Islam will prevail throughout the world. The Prophet (peace be upon him and his progeny) has given the good tiding in the above tradition.