וְשַׂ֣ר ׀ מַלְכ֣וּת פָּרַ֗ס עֹמֵ֤ד לְנֶגְדִּי֙ עֶשְׂרִ֣ים וְאֶחָ֣ד י֔וֹם וְהִנֵּ֣ה מִֽיכָאֵ֗ל אַחַ֛ד הַשָּׂרִ֥ים הָרִאשֹׁנִ֖ים בָּ֣א לְעָזְרֵ֑נִי וַאֲנִי֙ נוֹתַ֣רְתִּי שָׁ֔ם אֵ֖צֶל מַלְכֵ֥י פָרָֽס׃
But the prince of the kingdom of Persia withstood me one and twenty days; but, lo, Michael, one of the chief princes, came to help me; and I was left over there beside the kings of Persia.
Read kabbalistic (mystical) interpretation of Daniel 10:13: and classical mystical sources.