Daniel 10:4; Daniel 10:13

4 On the twenty-fourth day of the first month, while I was by the bank of the great river, that is, the Tigris,
13 "But the prince of the kingdom of Persia was withstanding me for twenty-one days; then behold, Michael, one of the chief princes, came to help me, for I had been left there with the kings of Persia.