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 nations and peoples 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)When Jesus called Himself the Son of Man, He was referring to this person. The Jewish leaders knew what He was saying and did not like it.
Then will appear the sign of the Son of Man in heaven. And then all the peoples of the earth will mourn when they see the Son of Man coming on the clouds of heaven, with power and great glory. (Matt. 24:30)Here the Son of Man is identified as the only-begotten Son.
Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up, that everyone who believes may have eternal life in him. For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. (John 3:14-16)