And measured them with a line - even with two lines - It has been generally conjectured that David, after he had conquered Moab, consigned two-thirds of the inhabitants to the sword; but I think the text will bear a meaning much more reputable to that king. The first clause of the verse seems to determine the sense; he measured them with a line, casting them down to the ground - to put to death, and with one line to keep alive. Death seems here to be referred to the cities by way of metaphor; and, from this view of the subject we may conclude that two-thirds of the cities, that is, the strong places of Moab, were erased; and not having strong places to trust to, the text adds, So the Moabites became David's servants, and brought gifts, i.e., were obliged to pay tribute. The word line may mean the same here as our rod, i.e., the instrument by which land is measured. There are various opinions on this verse, with which I shall not trouble the reader. Much may be seen in Calmet and Dodd.
David took great numbers of the Moabites prisoners of war, and made them lie down on the ground, and then divided them by a measuring line into three parts, putting two-thirds to death, and saving alive one-third. The cause of the war with the Moabites, who had been very friendly with David 1 Samuel 22:3-4, and of this severe treatment, is not known. But it seems likely, from the tone of Psalm 60:1-12 that David had met with some temporary reverse in his Syrian wars, and that the Moabites and Edomites had treacherously taken advantage of it, and perhaps tried to cut off his retreat.