Daniel 10:13-14

But the prince of the kingdom of Persia was standing in opposition to me for twenty-one days. Then, behold, Michael, one of the chief [of the celestial] princes, came to help me, for I had been left there with the kings of Persia. Now I have come to make you understand what will happen to your people in the latter days, for the vision is in regard to the days yet to come.”