Surely, the true religion with Allah is Islam. And those who were given the Book did not disagree but after knowledge had come to them, out of mutual envy. And whoso denies the Signs of Allah, then surely, Allah is Quick at reckoning. (3:20)
All religions inculcate belief in the Oneness of God and submission to His Will, yet it is only in Islam (which means complete submission) that the idea of submission to God’s Will has found its consummation; for complete submission requires complete manifestation of God’s attributes, and it is in Islam alone that such manifestation has taken place. So of all religious systems, Islam alone deserves to be called God’s own religion in the real sense of the term.
All true religions were indeed more or less Islam in their original form, and their adherents Muslims in the literal sense of the term, but not till the time when religion became complete in all its different aspects was it given the name of Al-Islam, which was reserved for the final Dispensation perfected in the Holy Quran.
This day I have perfected your religion for you and completed My favor upon you and have chosen for you Islam as religion. (5:4)