Psalms 78:49
He cast upon them the fierceness of his anger, wrath, and indignation, and trouble, by sending evil angels among them. He cast upon them the fierceness of his anger, wrath, and indignation, and trouble, by sending evil angels among them.
The psalm containing this verse recounts the rich blessings God bestowed on His people and their poor return for those benefits. It shows Israel constantly working against a good God. The fierceness of anger, wrath, indignation and trouble it describes was the sure result of their own disobedient course of action.
The evil angels in the verse carry out the enemy's work. Those struck by such rebuke and chastisement repented, but fell again under temptation, self-indulgence, and self-gratification. Applied to the work of gathering people, the verse warns that unless that work is followed up, Satan will use evil angels to undo it.