All prophets preached monotheism and had superior moral values and sincere faith. God reveals that His messengers were entrusted with calling their people to monotheism:

We sent a Messenger among every people saying: "Worship God and keep clear of all false deities..." (Quran 16: 36)

After the prophets, however, monotheism was gradually corrupted and altered by human beings. Thus, God would send a new messenger to recite His verses, warn them of the Day of Judgment and unite them again under monotheism. Following the corruption of the revelation brought by Prophet Moses (pbuh), Prophet Jesus (pbuh) was sent to call his people to God's oneness and to depart from their bigoted traditions, abandon their superstitions, and submit solely to God. For example:

And when Jesus came with the Clear Signs, he said: "I have come to you with wisdom and to clarify for you some of the things about which you have differed. Therefore have fear [and respect] of God and obey me. God is my Lord and your Lord, so worship Him. This is a straight path." (Quran 43: 63-64)

I come confirming the Torah I find already there, and to make lawful for you some of what was previously forbidden to you. I have brought you a Sign from your Lord. So have fear [and respect] of God and obey me. God is my Lord and your Lord, so worship Him. That is a straight path." (Quran 3: 50-51)

When Prophet Jesus (pbuh) began to lead his people and their religious leaders, many of whom had departed from the Mosaic Law, invented their own ideas of what was lawful and prohibited, and developed a formalist and bigoted form of religion, they mocked him and became hostile.

Despite mounting obstacles, the number of Prophet Jesus' (pbuh) followers rose rapidly, especially among the poor. In order to put an end to Prophet Jesus (pbuh) and his message, the local Roman administrators and several Jewish religious leaders set a trap for Prophet Jesus (pbuh) and eventually decided to crucify him. The Qur'an records our Lord's response to this move:

They [the unbelievers] plotted and God plotted. But God is the best of plotters. (Quran 3: 54)

Just as our Lord saved Prophet Abraham (pbuh) from the fire, He rescued Prophet Jesus (pbuh) from this trap by raising him to His presence:

And their saying: "We killed the Messiah, Jesus son of Mary, Messenger of God." They did not kill him and they did not crucify him, but it was made to seem so to them. Those who argue about him are in doubt about it. They have no real knowledge of it, just conjecture. But they certainly did not kill him." (Quran 4: 157)

Clearly, those who sought to kill Prophet Jesus (pbuh) failed. As is revealed in other verses of the Qur'an, Prophet Jesus (pbuh) did not die but is alive in God's presence. God has revealed that He foiled the plot against Prophet Jesus (pbuh), which serves as important evidence that the prophet is alive in His presence. Our Lord foiled the plot intended to kill Prophet Jesus (pbuh). The claims made by those who maintain that Prophet Jesus (pbuh) was killed consist of nothing more than speculation. The Romans, imagining that they were crucifying Prophet Jesus (pbuh), actually crucified someone else. God showed people someone who resembled Prophet Jesus (pbuh) and then raised him to His presence.  

Our Lord Has No Son

The basic logic behind trinitarianism is that Prophet Jesus (pbuh) is the son of God. However, God's names invalidate these claims, for in His capacity as the Lord of the Worlds, He is far removed from such comparisons ignorantly made by human beings. He is unsullied by any flaw or deficiency. The Qur'an reveals:

It is not fitting for God to have a son. Glory be to Him! When He decides on something, He just says to it: "Be!" and it is." (Quran 19: 35)

They say: "God has a son." Glory be to Him! He is the Rich beyond Need. Everything in the heavens and everything on Earth belongs to Him. Have you authority to say this, or are you saying about God that which you do not know? (Quran 10: 68)

It is enough for our Lord to say Be! for something to come into existence. All entities are His property and His creations. All things have bowed their heads to Him and surrendered to His infinite power and might:

...Everything in the heavens and Earth, willingly or unwillingly, submits to Him... (Quran 3: 83)

God is free of all causes, because He created whatever exists and happens, as well as their underlying causes. Everything happens in accordance with specific causes. For example, birth, death, learning, and ageing happen as the result of specific causes, such as time and space. Human beings live dependent on time and space. But our Lord is independent of time and space. He, Himself created time and space. It is our Lord Who created fatherhood, being a son, and having children, which are features peculiar to human life. Therefore, those who say that "God has a son" forget our Lord's incomparable names and think within the bounds of their own limited human perceptions.

They say: "God has a son." Glory be to Him! No, everything in the heavens and Earth belongs to Him. Everything is obedient to Him, the Originator of the heavens and Earth. When He decides on something, He just says to it, "Be!" and it is. (Quran 2:116-117)

They say: "The All-Merciful has a son." They have devised a monstrous thing. The heavens are all but rent apart, Earth split open, and the mountains brought crashing down at their ascription of a son to the All-Merciful! It is not fitting for the All-Merciful to have a son. There is no one in the heavens and Earth who will not come to the All-Merciful as a servant. He has counted them and numbered them precisely. Each of them will come to Him on the Day of Resurrection all alone." (Quran 19: 88-95)  

The Messiah would never disdain to be a servant to God, nor would the angels near to Him. If any do disdain to worship Him and grow arrogant, He will in any case gather them all to Him. (Quran 4:172)

As revealed in the verse, Prophet Jesus (pbuh) is a very devout individual who is proud to fulfill his duty of service to God and submit to Him fully. All references to his supposed divinity were produced long after he was raised to God's presence. Our Almighty Lord possesses complete dominion over all beings. Everything apart from Him needs our Lord to exist and to survive.

God created the universe from nothing. All living things are born and die, and everything has an allotted life span. There is nothing in the universe that will not come to an end one day, nor any living thing that will not finally die. As the Qur'an reveals, however, "God is the First and Last" (Quran 57: 3). In other words, He has no beginning and no end. He existed before everything and will continue to exist after everything. Before the universe and its contents were created, there was only God; after the universe and its contents cease to exist, there will be only God. God, the Creator of life and time, is independent of all features of matter.

It is revealed that Prophet Jesus (pbuh) is mortal, and that like all other human beings He will be resurrected in the Hereafter:

Peace be upon me the day I was born, the day I die, and the day I am raised up again alive." (Quran 19: 33)

God created him, gave him an allotted span on Earth to preach monotheism, and then raised him to His presence to save him from those who plotted against him. When the time appointed by God comes, Prophet Jesus (pbuh) will return to Earth and, in the manner decreed by God, complete his duties as messenger, for God has shaped his entire destiny, just as He has done for all people. God created every miracle performed by Prophet Jesus (pbuh), and allowed him to display them through His mercy. Throughout his earthly life, Prophet Jesus (pbuh) expressed his deep faith in God and called people to His straight path, as the following verse states:

God is my Lord and your Lord, so worship Him. This is a straight path. (Quran 19:36)

Prophet John's (pbuh) birth was also a miracle from God. Our Lord imparted a blessing by giving Prophet Jesus (pbuh) extraordinary miracles (God gave all the prophets miracles as an evidence to their massages). His life was full of miracles, from his birth until his elevation to God's presence. One of these miracles was that he was born of a virgin. The birth of Prophet Jesus (pbuh) is truly a great miracle of our Lord. The Qur'an describes how Angel Gabriel appeared to Mary as a handsome, well-built man and informed her of God's will for her: although no man had ever touched her, by the will of God she became with child with Prophet Jesus (pbuh). Her pregnancy took place in a miraculous manner, independent of any earthly cause:

She asked: "How can I have a son when no man has touched me and I am not an unchaste woman?" He [Gabriel] said: "It will be so. Your Lord says: 'That is easy for Me. It is so that We can make him a Sign for humanity and a mercy from Us.' It is a matter already decreed." So she conceived him and withdrew with him to a distant place. (Quran 19: 20-22)

As can be seen from the clear language in this verse, Prophet Jesus (pbuh) came into the world by means of a creation outside the known causes, without a father.

Reason refuses to accept a man who was born of a woman, suffered from human wants, ignorance and limitations, and gradually grew in stature, power and wisdom, like all other human beings, as God. To put human limitations upon God and to believe in His incarnation in a human body is to deny the perfection of God.

The creation of Prophet Adam (pbuh)

The extraordinary creation of Prophet John (pbuh) and Prophet Adam (pbuh) are proof that Prophet Jesus (pbuh) was not created to be part of a triune God. According to the Qur'an, Prophet Adam (pbuh) was also created in a miraculous manner.

... when your Lord said to the angels: "I am creating a human being out of dried clay formed from fetid black mud. When I have formed him and breathed My Spirit into him, fall down in prostration in front of him." (Quran 15: 28-29)

The creation of Prophet Adam (pbuh) is also similar to that of Prophet Jesus (pbuh):

The likeness of Jesus in God's sight is the same as that of Adam. He created him from earth and then He said to him "Be!" and he was. It is the truth from your Lord, so do not be among the doubters. (Quran 3: 59-60)

In these verses, God reveals that He created Prophet Adam (pbuh) and Prophet Jesus (pbuh) in a similar manner: Prophet Adam (pbuh) was created out of clay and had no ancestors, and Prophet Jesus (pbuh) had no father. Both of them were created through God's command of Be! This great truth, which leaves no room for doubt, makes it clear that both prophets were God's servants who, despite their exalted status, were still completely dependent upon Him to meet all of their needs.

Prophet Jesus (pbuh) is only a prophet

The Qur'an mentions many subjects, such as the birth of Prophet Jesus (pbuh), some events in his life, his family, and the people around him. He is depicted as the Messiah, son of Mary and prophet of God.

Throughout his life, Prophet Jesus (pbuh), sent to lead a community that had gone astray to the true path, called on his people to have sincere faith and submit themselves to God. It also appears, from various verses of the Qur'an that he acted as a guide to those who had fallen into religious disagreements. Certain New Testament passages indicate that he primarily called on hypocritical, insincere religious figures and those who deceived the public behind a mask of devotion to cease what they were doing and believe in God. The Qur'an reveals this in the following terms:

And when Jesus came with the Clear Signs, he said: "I have come to you with Wisdom and to clarify for you some of the things about which you have differed. Therefore, have fear [and respect] of God and obey me." (Quran 43: 63)

Like all of the prophets, Prophet Jesus (pbuh) targeted moral degeneration and atheism. He told people to abandon their injustice, immorality, and superstitions; to live by God's ordained moral values and for His good pleasure alone; to fear [and respect], love, and submit to God; and to turn away from superstitious laws and hollow traditions, to worship only God, and to turn to Him at all times. The miracles that he performed revealed that God had chosen him as His messenger, and that He supported him with knowledge and power. His depth of faith, high moral values, superior understanding, and wise explanations inspired great admiration among his people.

Prophet Jesus (pbuh) displayed great patience with his opponents, put his trust in God and continued to inform his people of God's revelation despite the hostile environment in which he was living. Although he had very few helpers, he endeavored to restore his people's religion to its essence and cleanse it of all meaningless rituals and superstitious practices. Thanks to his superior understanding and wisdom vouchsafed to him by our Lord, he made highly affective addresses to the Children of Israel and told them very wise parables.

 Source (edited):

 http://www.harunyahya.com/books/faith/Jesus_prophet/not_a_son01.php