He smote Moab. — David’s former friendly relations with Moab (probably connected with his own descent from Ruth), are mentioned in 1 Samuel 22:3-4. The cause of his entire change of bearing towards them is not certainly known, but according to Jewish tradition the Moabites had proved false to their trust, and had put to death David’s father and mother. This is not unlikely, as his parents are never mentioned again after they were left in Moab. Others think that the Moabites had been guilty of some treachery towards David in his war with the Syrians and Ammonites. The two suppositions are quite consistent, and both may have been true. Many writers see in this conquest at least a partial fulfilment of the prophecy in Numbers 24:17.
With two lines. — This expression with the “one full line” of the next clause is equivalent to saying that David measured off the bodies of his prostrate enemies with a line divided into three equal parts. When they had been made to lie down upon the ground, side by side, the line was stretched over them. Such as were found under the two first parts of it were put to death, those under the third part were spared, thus two-thirds of all the Moabite men perished. There is no mention of this in 1 Chronicles 18:2.
Brought gifts. — A frequent euphemism for paid tribute. (Comp. 2 Samuel 8:6.)