In evangelistic dialogue with people, I am sometimes asked why I am a Christian and not a Muslim. Below are the two most important reasons why I reject Islam in favor of the Christian faith.
1) Jesus is the final revelation of God and the sole mediator of salvation to his people.
2) Jesus and all the apostles warned of future false teachers.
1) Christianity teaches that God can be known definitively and personally in Jesus Christ: “No one has ever seen God; the only God, who is at the Father’s side, he has made him known” (John 1:18); “Whoever has seen me has seen the Father” (John 14:9). Jesus Christ is the exact and final revelation of who God is. Hebrews. 1:1-3 says “Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days he has spoken to us by his Son, whom he appointed the heir of all things, through whom also he created the world. He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power.(Heb. 1:1-3)” Colossians 1 says he is the image of the invisible God (Col. 1:15). His coming was planned by God for our salvation: “But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons. (Gal. 4:4)” Furthermore, the acts and jurisdiction of salvation are now solely based upon him (“For there is one God, and there is one mediator between God and men, the man Christ Jesus. [1 Tim. 2:5] and Acts. 4:12;John 14:16). Christianity is sufficient because Jesus Christ is sufficient.
2) Jesus himself warned against false prophets and false teachers who would come trying to deceive people away from the truth (Matthew7:15; 24:11, 24; Mark 13:22; Luke 6:26). All the apostles warned that false teachers, preachers, and prophets would try to deceive Christians and the world about Jesus Christ: Peter (2 Pet. 2:1), Jude (Jude 1), John (1 John 4:1; 2 John 1:7-11; Rev. 16:13), Paul (Rom. 16:17; 1 Tim. 4:1-5; 2 Cor. 11:13-15), Luke (Acts 20:29), and a host of other verses. Paul says in Galatians 1:8-9 that “But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed. As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be accursed.” Paul is basically saying “If I come along and preach to you a different message than the one I already preached from the apostles and Jesus OR if an angel from heaven comes and preaches a different gospel than the one about Jesus Christ- let them go to hell! You can understand why Christians do not accept Islam.
Christianity and Islam are fundamentally different on theology proper (the study of God), Christology (the study of the person of Christ), anthropology (study of man [i.e. Christianity teaches man is made in God’s image]), hamartiology (the study of sin and its effects), bibliology (the study of the sacred scriptures),and especially soteriology (study of salvation and how one “obtains” it). There is a vast discord between what Christianity teaches on the doctrines of the Word of God, God, man, Christ and the Holy Spirit, the application of redemption, the Church, and the future and what Islam teaches on those subjects. If Islam and Christianity are cousins in the faith, they are third or fourth cousins. The closest other “religions” to Christianity would be the cults (Jehovah’s Witness, Mormonism, Seventh Day Adventists) and maybe Judaism. It basically boils down to a religion of grace where God works for his glory and your joy and a religion of works where you joylessly work for God trying to obtain glory. As John Macarthur said in his book The Gospel According to Jesus:
Men have always stumbled over the simplicity of salvation (in Christianity). That is why there are so many cults [Islam is an example]. Each one has a unique slant on the doctrine of salvation, each corrupting the simplicity of the gospel revealed in God’s Word (2 Cor. 11:3) by espousing salvation by human works. Each one of the major cults claims to have a key that unlocks the secret of salvation, yet they are all alike in propagating self-righteous achievement as the way to God. From start to finish, God’s Word disproves them all, and in a wonderfully consistent way. Its message, woven through sixty-six books, written over a span of fifteen hundred years by more than forty different authors, is marvelously unified and congruous. The message is simply that God graciously saves repentant sinners who come to him in faith. There is no secret there, no mystery, no obscurity, and no complexity.
Jesus said “It is finished.” Who am I to try to redo what he accomplished? Who am I to say what he did was not worthy or sufficient enough for my salvation? Who am I to add my own filthy rags atop his majestic claim of cruciform glory? God has not only come down from the mountain. He died on a hill outside of Jerusalem (Heb. 13:12).