David’s victory over the Moabites is a fulfillment of the promise and prophecy made in Numbers 24:17–19,1 and it serves to highlight the faithfulness of the Lord.2 When he puts two-thirds of their men to death, he does so to ensure that they will not be a threat to Israel going forward and that they will still be able to provide some kind of tribute.3 The Moabites will remain subject to Israel until the death of Ahab (2 Kings 3:4–5).4
2 Il battit les Moabites, et il les mesura avec un cordeau, en les faisant coucher par terre; il en mesura deux cordeaux pour les livrer à la mort, et un plein cordeau pour leur laisser la vie. Et les Moabites furent assujettis à David, et lui payèrent un tribut.