The phrase “son of man” occurs in 178 verses in the Bible. Sometimes it’s written as “son of man” and other times, as “Son of man.”
When used as Son of man, the references are to Jesus, as seen in all four gospels (28 times in Matthew; 13 times in Mark; 25 times in Luke; and 12 times in John). It’s also written this way in Psalm 80:17, Daniel 7:13, and Acts 7:56, again implying Jesus.
So, how can the Son of man refer to Jesus, while son of man refer to people?
Here are my thoughts: Jesus is the only son of God. We, as his church, are his bride. Therefore, through this spiritual marriage, we also become children of God, that is, sons of God, or to slide back into the euphemism, sons of man.