13. prince of . . . Persia--the angel of darkness that represented the Persian world power, to which Israel was then subject. This verse gives the reason why, though Daniel's "words were heard from the first day" (Da 10:12), the good angel did not come to him until more than three weeks had elapsed (Da 10:4).
      one and twenty days--answering to the three weeks of Daniel's mourning (Da 10:2).
      Michael--that is, "Who is like God?" Though an archangel, "one of the chief princes," Michael was not to be compared to God.
      help me--Michael, as patron of Israel before God (Da 10:21; 12:1), "helped" to influence the Persian king to permit the Jews' return to Jerusalem.
      I remained--I was detained there with the kings of Persia, that is, with the angel of the Persian rulers, with whom I had to contend, and from whom I should not have got free, but for the help of Michael. GESENIUS translates, "I obtained the ascendency," that is, I gained my point against the adverse angel of Persia, so as to influence the Persian authorities to favor Israel's restoration.

JFB.