And the third angel poured out his bowl upon the rivers and fountains of waters; and they became blood.
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Bede
AD 735
waters: And they also who pretend that they give to drink sweet things, in order that they may pour out their poison upon the incautious, will be punished with the worthy retribution of a continual plague.
angel: In the angel of the waters he speaks of all the angels of the peoples, who in inner affection are united in singing the praises of God; for that in avenging the blood of His servants, He has made their murderers to drink of death. <a
Upon the rivers. That is, on the Roman provinces in Italy, and Rome itself. This is the last stroke employed by the Almighty for the total destruction of Rome. The divine judgment being executed, the Angel of the waters, that is, the Angel that presided over the Roman states, cries out, (ver. 5, 6.) thou art just (Pastorini)