Charles Ellicott Commentary 1 Chronicles 18:13

"And he put garrisons in Edom; and all the Edomites became servants to David. And Jehovah gave victory to David whithersoever he went." — 1 Chronicles 18:13 (ASV)

And he put garrisons (or “prefects,” 1 Chronicles 18:6) in Edom. —Samuel adds, in all Edom he set garrisons, thus marking the complete subjugation of the country.

Thus the Lord preserved David. —See 1 Chronicles 18:6. David was victorious on all sides, north (1 Chronicles 18:3–8), and south, and east, and west (1 Chronicles 18:11). The six peoples whom he reduced had been the foes of his ill-fated predecessor (1 Samuel 14:47–48).