Daniel 6:28
"So this Daniel prospered in the reign of Darius, and in the reign of Cyrus the Persian."
Cross References (ranked by relevance)
Daniel 1:21
And Daniel continued even unto the first year of king Cyrus.
Daniel 10:1
In the third year of Cyrus king of Persia a thing was revealed unto Daniel, whose name was called Belteshazzar; and the thing was true, but the time appointed was long: and he understood the thing, and had understanding of the vision.