Revelation 9:15 in the World English Bible
The four angels were freed who had been prepared for that hour and day and month and year, so that they might kill one third of mankind.
Context
14 Saying to the sixth angel which had the trumpet, Loose the four angels which are bound in the great river Euphrates.
15 And the four angels were loosed, which were prepared for an hour, and a day, and a month, and a year, for to slay the third part of men.
16 And the number of the army of the horsemen were two hundred thousand thousand: and I heard the number of them.