TWH: One of the types of uses in the Old Testament that is usually considered entirely human (I'm sure there is someone somewhere who argues for a messianic interpretation of some of them) is the Hebrew expression "[. . .] man, [. . .] son of man." One example is Ps. 144:3: "O Lord, what is man, that you take knowledge of him? Or the son of man, that you think of him?" Another is Isa. 51:12: "I, even I, am he who comforts you. Who are you that you are afraid of man who dies and of the son of man who is made like grass?" Notice the progression from talking about man, then son of man. This shows up elsewhere in the Old Testament (e.g., Ps. 8:4; Isa. 56:2). To this type of expression we can add the direct address "son of man" that is ascribed to prophets, also human. This use is found almost exclusively in Ezekiel (see Ezek. 2:1 and numerous other examples throughout his prophecy); only one such use is found in Daniel (8:17). The messianic usage of "Son of Man" is tied to a single passage in Daniel:
"I kept looking in the night visions, and behold, with the clouds of heaven, one like a Son of Man was coming. And he came up to the Ancient of Days and was presented before him. And to him was given dominion, glory, and a kingdom, so that all the peoples, nations, and men of every language might serve him. His dominion is an everlasting dominion that will not pass away. And his kingdom is one that will not be destroyed." (Dan. 7:13–14)There's always a debate going on about the identity of the "Son of Man" in Daniel. Some have argued that he is a symbol for the people of God; some that he is a heavenly being, but not divine; some that he is divine. The question I want to address is why Jesus used this title in reference to himself. If he is the "Son of God," then why didn't he just refer to himself as the Son exclusively, or why not as the Christ, or why not in some other way?
The title "Son of Man" was closely associated with the role of a prophet, as we mentioned above. Jesus was the prophet that was promised through Moses (Deut. 18:15). This is the same one that the crowds deduced that Jesus was in John 6:
“When therefore the people saw the sign that he had performed, they said, ‘This is truly the Prophet who is to come into the world.’ Jesus then, perceiving that they were intent on trying to take him by force and install him as king, withdrew again to the mountain by himself alone” (John 6:14–15).It's clear from that passage that the Jewish people did not draw a sharp distinction between the promised prophet of Deuteronomy and the Messiah. Their reaction to attempt to install Jesus as king is strong enough evidence for anyone to arrive at that conclusion. But what about the title "Son of Man"? R. G. Hamerton-Kelly is one who has put forth the position that "Jesus referred to himself as the Son of Man in contexts in which his authority was challenged, or his person rejected" (Pre-Existence, Wisdom, and The Son of Man, 96). He continues: "He implied by the title that he would appear as the heavenly advocate in the future, and then men would see who he really is" (96). Of course, there's an issue at times in these discussions as to what verses some scholars actually consider to be historical or part of the teaching of the Jesus of history. If someone has whittled away at the text, then there's a chance they end up looking at a collection of Jesus' sayings that is different from another person who accepts as historical a passage not in that collection. But what about the argument that Jesus only used this title in contexts of confrontation or rejection? Let's think about that for a moment, using only the Gospel of Matthew as a test case.
The first use of "Son of Man" in Matthew is found in 8:20: "The foxes have holes and the birds of the air have nests, but the Son of Man has nowhere to lay his head." No further details are provided in the context about whether or not the scribe (he was also a disciple of Jesus at that point, given the use of ἕτερος in 8:21) who came to Jesus and wanted to follow him actually gave it all up and began following Jesus. This seems like the most difficult passage to fit into the view that Jesus only used the title in confrontation or rejection contexts. There's no question that there was conflict in most of the other passages leading up to the ultimate rejection of Jesus by the religious elite in Matthew 13: 9:6; 10:23; 11:19; 12:8, 32, 40. The use of the Son of Man title in Matthew 13 (vv. 37–41) with the parables could certainly fall into this category of conflict, since Jesus switched to parables as a result of the people's rejection of him. But there's another connection and that is the definite picture of the his return to earth as judge.
The figure of the Son of Man was of particular interest to Jesus and the nation of Israel. The people were looking for this individual. This is why we see Jesus begin his inquiry of the disciples in Caesarea Philippi with the following question: "Who do people say that the Son of Man is?" (Matt. 16:13). They respond with the answers John the Baptist, Elijah, Jeremiah, or one of the prophets (Matt. 16:14). This could very well be one of the reasons that Jesus opted for this title during his ministry. There was a readiness in the hearts and minds when it came to this particular individual. Sure they were were looking for the Christ, the heir to the David throne, but this particular passage would have harmonized with them like none other. The Son of Man was going to come and judge the wicked, and to him would be given the kingdom, meaning he had to be the heir to the Davidic throne. The presence of the title in the Olivet Discourse (Matthew 24) becomes then the most expected place to find such a title.
Another reason that we ought to point out for why Jesus used this title––one we can't help but make––is that Jesus taught strategically throughout his ministry so as not to hasten an arrest and punishment. That was all going to come, but in due time––at the time fixed by the Godhead––and teaching in the third person allowed him to avoid scenarios that would have sped up the events of his ministry, even cutting out a significant and necessary portion of that ministry, namely preparing his closest disciples for the work that they would need to do once he returned to the right hand of the Father and issuing a call of repentance to the people of Israel.