Jamieson, Fausset and Brown on Amos 5:9

9. strengtheneth the spoiled--literally, "spoil" or "devastation": hence the "person spoiled." Winer, Maurer, and the best modern critics translate, "maketh devastation (or destruction) suddenly to arise," literally, "maketh it to gleam forth like the dawn." Ancient versions support English Version. The Hebrew is elsewhere used, to make, to shine, to make glad: and as English Version here (Psa 39:13), "recover strength."

the spoiled shall come--"devastation," or "destruction shall come upon" [Maurer]. English Version expresses that, strong as Israel fancies herself after the successes of Jeroboam II (2Ki 14:25), even the weakest can be made by God to prevail against the strong.