The emergence of Islam returned the Abrahamic monotheism to its original purity. Islam perceives the doctrine of trinity and incarnation as a veil cast upon the complete reality of Divine unity. Nothing should compromise divine unity. God is the absolute, the One without condition, and above all relations.
The distinguishable feature of the Islamic faith from other monotheistic religions is its insistence on absolute monotheism. Islam entirely opposes any association concerning God and the notion that Jesus, the Messenger of God, was God himself. God states in the Quran, “It is not for a man, that Allah should give him [Jesus] the Book [Gospel], and judgment and apostleship, and yet he [Jesus] should say to people, “Worship me rather than Allah,” but rather [he would say] “Be a godly people, because of your teaching the Book and because of studying it [yourselves].” (3:79)
Muslims believe that Jesus was a human prophet who was divinely inspired by God, and they consider him to be a servant and conveyer of God’s message and neither the Old Testament nor the New Testament mentions that Jesus was the son of God.
Barbara Brown, a contemporary American scholar, supports this idea with the following statement: The doctrine of divinity states that Jesus is the Son of God, the Word of God made flesh. Even though Jesus himself never claimed to be divine, Paul gave him this attribute for one reason – to gain converts among the Gentiles. The Gentiles were pagans who were used to worshipping gods that had wonderful legends and myths behind them. Several of the pagan deities of the time such as Mithras, Adonis, Attis, and Osiris were the offspring of a supreme ruling idol and each had died a violent death at a young age, coming back to life a short time later in order to save their people. Paul took this into account, giving the pagans something similar in Christianity. He attributed divinity to Jesus, saying he was the Son of God, the Supreme, and that he too had died for their sins. In doing so, Paul compromised the teaching of Jesus with pagan beliefs in order to make Christianity more acceptable to the Gentiles.
The term “son of God” was not something new. However, it had been used in the Old Testament to refer to David (Saul 2:7) and his son Solomon (I Chronicles 22:100) and to refer to Adam (Luke 3:38) in the New Testament. In his famous Sermon on the Mount, detailed in Matthew 5, Jesus tells his listeners, “Blessed are the peacemakers, for they shall be called sons of God.” In all cases, the term “son of God” was not meant to be applied literally but to signify love and affection from God to the righteous. “Son of God” means a special closeness to God, not to be of God. After all, people are sons [spiritual dependants] of God, and God is the creator of all life.
Christians who lived during the time of Jesus believed that Jesus was divinely inspired by God and not God himself. However, after the ascension of Jesus to heaven, Saint Paul, who was deeply influenced by Roman paganism, wanted his preaching of Christianity to be more appealing to the Gentiles and thus, he compromised the teachings of Jesus by adopting certain pagan ideas and interpolating them into Christianity. Even though it was not part of the original teachings of Jesus, the idea of the trinity has widely spread.
 Also see Quran 5:72-75.
 Barbara Brown, A Closer Look at Christianity