Revelation 9:14
It said to the sixth angel with the trumpet, "Release the four angels who are tied up at the great Euphrates River."
Revelation 16:12
And the sixth [angel] poured out his bowl on the great Euphrates River and its water was dried up, so that the road would be prepared for the kings from the east [to travel on].
Revelation 7:1
After this I saw four angels standing at the four corners of the earth. They were holding back the four winds of the earth so that no wind would blow on the earth, on the ocean or on any tree.
Revelation 8:2
And I saw the seven angels who were standing in front of God, and they were given seven trumpets.
Revelation 8:6
And the seven angels who had the seven trumpets prepared to blow them.
Revelation 9:15
And the four angels who had been ready for this hour and day and month and year were [now] released to kill one third of mankind.