דברי הימים א, פרק י״ח, פסוק ב׳

The historical account of the military campaign against Moab is presented very briefly, assuming the reader will fill in the missing details from the parallel record found in the Book of Samuel [מלבי״ם]. That expanded account reveals the severe extent of the punishment inflicted upon the defeated nation. David measured the Moabite captives with a rope, issuing an order to put two-thirds of them to death while keeping the remaining one-third alive [רלב״ג].

Following their defeat, the surviving Moabites became servants to David and were required to bring him tribute. This ongoing payment of taxes served as a practical expression of their complete submission and subjugation under his rule [ביאור שטיינזלץ].