Revelation 9:15

15. For an hour Our version gives the indefinite article instead of the definite the, and thus misleads some interpreters into a very devious course. They have taken these notes of time as telling how long the war was to last, and then, having calculated, symbolically, the length of the period, have endeavoured to find a war of the exact length in actual history. But these time-words indicate not the length of any one war, but the precise instant when, by divine permission, they commence. At the right hour, in its due place in month and year, the minister of vengeance springs forth.

For to slay The error-demons only torment; the war-demons slay.

Third part of men The divine number three indicates, like the five months of Revelation 9:5, (where see note,) a divinely-fixed limitation. It of course implies no literal fulfilment as to number.