Allah Says in the Qur'an in the interpretation of the meaning:

"Let there be no compulsion in Religion: truth stands out clear from error: whoever rejects evil and believes in Allah (one God) has grasped the most trustworthy hand hold, that never breaks. and Allah hears, and knows all things." 
(Qur'an, Al-Baqarah 2:256)

Islam is not a new religion, but the same truth that God revealed through all His prophets to every people. God tells us in the Qur'an:

"Say: we believe in God and in what has be...