Jesus would frequently refer to himself as the 'Son of Man'. One example of this was when he healed the paralysed man who was lowered down through the roof of the house.
Immediately Jesus knew in his spirit that this was what they were thinking in their hearts, and he said to them, "Why are you thinking these things? Which is easier: to say to the paralytic, 'Your sins are forgiven,' or to say, 'Get up, take your mat and walk'? But that you may know that the Son of Man has authority on earth to forgive sins...." He said to the paralytic, "I tell you, get up, take your mat and go home." He got up, took his mat and walked out in full view of them all. This amazed everyone and they praised God, saying, "We have never seen anything like this!" (Mk 2:8-12)
What did he mean by this? Was Jesus affirming his humanity by these words? Or did it mean something else?
Let's look at another time when he used this phrase, this time during his trail before the Sanhredren.
The high priest said to him, "I charge you under oath by the living God: Tell us if you are the Christ, the Son of God."
"Yes, it is as you say," Jesus replied. "But I say to all of you: In the future you will see the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of heaven."
Then the high priest tore his clothes and said, "He has spoken blasphemy! Why do we need any more witnesses? Look, now you have heard the blasphemy." (Mt 26:63-65)
Here Jesus quotes the prophet Daniel when he states that the Son of Man will come on the clouds of heaven.
In my vision at night I looked, and there before me was one like a son of man, coming with the clouds of heaven. He approached the Ancient of Days and was led into his presence. He was given authority, glory and sovereign power; all peoples, nations and men of every language worshiped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed. (Dan 7:13-14)
This was well understood by the Jews of the time that this was a divine image. The Son of Man on the clouds of heaven was understood to be a divine figure, and so for Jesus to claim this title for himself, was in effect a claim to be God.
The high priest at the trial clearly understood Jesus' claim. He immediately accused Jesus of blasphemy, and stated that there was no need for further evidence. Jesus had just claimed to be God, and so in their eyes was guilty of blasphemy.
So Jesus' use of the title "Son of Man" was not predominantly used to assert his humanity. He used it in reference to Daniel's prophecy and was claiming to be God, albeit in a roundabout manner.
Comments
I understand it enabled him to basically say he was Son of God without saying it, and so avoid being charged of blasphemy. I'm not sure if he ever explicitly says "I am the Son of God", he merely responds to people askign if he is "you say taht I am". I may be wrong, but if I'm not it shows just how seriiusly Jesus took our duty to obey the law of the land. And the miracle is he still got his message through clearly.