Son of man came to serve refers to a specific episode in the New Testament

New Testament

The New Testament is the second major division of the Christian biblical canon, the first such division being the much longer Old Testament....

.
In the Gospel of Matthew

Gospel of Matthew

The Gospel According to Matthew is one of the four canonical gospels, one of the three synoptic gospels, and the first book of the New Testament. It tells of the life, ministry, death, and resurrection of Jesus of Nazareth...

 , and the Gospel of Mark

Gospel of Mark

The Gospel According to Mark , commonly shortened to the Gospel of Mark or simply Mark, is the second book of the New Testament. This canonical account of the life of Jesus of Nazareth is one of the three synoptic gospels. It was thought to be an epitome, which accounts for its place as the second...

  Jesus explains that he "came as Son of man to give his life as ransom".The ransom paid by the Son of man is an element of a common doctrine of atonement in Christianity.

In the Gospel of this episode takes place shortly after
Jesus predicts his death

Jesus predicts his death

Jesus predicts his death three times in the New Testament, the first two occasions building up to the final prediction of his crucifixion. The final prediction episode appears in all three Synoptic Gospels, in the Gospel of Matthew , the Gospel of Mark and the Gospel of Luke...

, and then says:

"You know that those who are regarded as rulers of the Gentiles lord it over them, and their high officials exercise authority over them. Not so with you. Instead, whoever wants to become great among you must be your servant, and whoever wants to be first must be slave of all. For even the Son of Man did not come to be served, but to serve, and to give his life as a ransom for many."

The identification of Jesus with the Son of man

Son of man

The phrase son of man is a primarily Semitic idiom that originated in Ancient Mesopotamia, used to denote humanity or self. The phrase is also used in Judaism and Christianity. The phrase used in the Greek, translated as Son of man is ὁ υἱὸς τοὺ ἀνθρώπου...

, in the context of the Book of Daniel

Book of Daniel

The Book of Daniel is a book in the Hebrew Bible. The book tells of how Daniel, and his Judean companions, were inducted into Babylon during Jewish exile, and how their positions elevated in the court of Nebuchadnezzar. The court tales span events that occur during the reigns of Nebuchadnezzar,...

 (7:13-14) places the death of Jesus and the ransom he pays at a higher level of prominence than other prophets and martyrs, even his contemporary John the Baptist

John the Baptist

John the Baptist was an itinerant preacher and a major religious figure mentioned in the Canonical gospels. He is described in the Gospel of Luke as a relative of Jesus, who led a movement of baptism at the Jordan River...

. Later in the New Testament account, in , when Jesus considers himself the Son of Man

Son of man

The phrase son of man is a primarily Semitic idiom that originated in Ancient Mesopotamia, used to denote humanity or self. The phrase is also used in Judaism and Christianity. The phrase used in the Greek, translated as Son of man is ὁ υἱὸς τοὺ ἀνθρώπου...

 spoken of in the Book of Daniel

Book of Daniel

The Book of Daniel is a book in the Hebrew Bible. The book tells of how Daniel, and his Judean companions, were inducted into Babylon during Jewish exile, and how their positions elevated in the court of Nebuchadnezzar. The court tales span events that occur during the reigns of Nebuchadnezzar,...

, the Jewish high priests accuse him of blasphemy.