Why describe the powerful angelic Prince as 'like a son of man' which has been argued effectively to imply human frailty in Daniel.
I think that is a bit of a Christian idea. Jews and the Hasmoneans didn't have the same view.
First, the term chebar actually means "like" as in "similar to" or "about" as in "something around the likes of." It doesn't refer to the quality of the subject, as if the subject is the same or necessarily shares something with what is being described.
It appears at Daniel 5:31 in reference to telling an age:
And Darius the Mede received the kingdom, being about [chebar] sixty-two years old.
The vision is connected to the ideas in chapter 12. But Michael is neither an "angel" in the Christian sense* nor the "messiah." Michael is the "dominion" or the authority or autonomy that the Hasomonean kings believed God had given them once they had received their Temple back from Antiochus. He is kind of like an excuse, to put it lightly.
Recall, these are Levites. Some of the Hasmoneans were part of the priesthood, from which came the high priest. So when time came to anoint a king, they knew the Torah and what is said about restrictions regarding rulership. They should have stopped their own family from taking the crown.
Instead, they anointed their brothers and put them on the throne. The high priest, the one who was supposed to know and uphold the Law for the people, was the only one who could anoint the king if there was no authorized prophet to do so. No one else could. Thus it was corrupt from the beginning.
How does one, therefore, legitimize an illegitimate dynasty that, according to Torah, is against the Law?
You write an oracle (as if you were a prophet) in which the Ancient of Days gives power to what was at the time believed to be the Prince guaradian of the Jews: Michael the Archangel.
In the vision of Daniel 7, the vision is of four succeeding kingdoms: Babylon, Media, Persia, and Greece.
When we get to verses 7-8, we come to the kings of the Seleucid empire. The little horn is Antiochus IV Epiphanes who usurped the throne and persecuted the Jews.
The writing of the apocalypse, of course, is contemporary with the events, usually after. When the Jews receive access to their Temple again and freedom to worship, the vision of "the son of man" that gains access to "the Ancient of Days" is written.
Is this "son of man" figure "the Jews"? Yes. Is he also "Michael the Archangel"? Yes, because he represents the Jews. Is this the Hasmoneans? Yes, because this was how they legitimized breaking the Mosaic Law to anoint their own brothers as kings when they as priests knew Levites had no right to rule as kings. Is this the "messiah"? There was no "messiah" teaching officially yet, but eventually the Hasmonean view of "Michael" was abandoned because of what they did and the Jews accepted a general "messiah" view of the text.
By the time the Herodian Temple stood, the Greek version of Daniel was popular reading. There were many explanations of Daniel, many views of "the son of man." And there was finally a full-fleshed out belief in the Messiah.
What there wasn't was a belief in the Hasmonean dynasty or its original ideals, teachings, or even the way it celebrated Chanukah (for a time then and after rabbis tried to stop it). The Christian movement and the Bar Kokhba Revolt only made it loose favor in the eyes of the Jewish sages and teachers. The Book of Daniel barely made it into the Hebrew canon.
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*-I could spend too much time trying to reframe something that would only leave people so confused. There are very few concrete things in Judaism. Angels is not one of them. Suffice to say: Christian angels are one thing, Jewish angels another. Apples, oranges. Best to leave it there for now.