And I heard the angel of the waters... — That is, the angel who was set over the waters, or the angel who is, on the heavenly side, representative of the waters. (See Excursus A: On the Angels.) The angel acknowledges God’s righteousness. Thou art righteous... because Thou didst judge these things — i.e., because of the righteous law which these judgments manifested.
Related Commentaries of Revelation 16:5
Revelation 16:5
5 And I heard the angel of the waters say, Thou art righteous, O Lord, which art, and wast, and shalt be, because thou hast judged thus.