Amos 5:3 - Albert Barnes' Notes on the Bible

The city that went out by a thousand - (that is, probably that sent out a thousand fighting men, as the word “went out” is often used for, “went out” to fight,) “shall have” literally, “shall retain, an hundred.” She was to be decimated. Only, the tenth alone was to be reserved alive; the nine-tenths were to be destroyed. And this, alike in larger places and in the small. The city “that went forth an hundred shall retain ten.” Smaller places escape for their obscurity, the larger from their strength and situation. One common doom was to befall all. Out of all that multitude, one tithe alone was to he preserved , “dedicated to God,” that remnant which God always promised to reserve.