He smote Moab; for although the king of Moab, out of hatred to Saul, pretended some kindness to David, and gave protection to his parents, 1 Samuel 22:3,4; yet the Moabites were perpetual and sworn enemies to the Israelites, who therefore were forbidden to admit them into the congregation of the Lord, and to seek their peace and prosperity, Deuteronomy 23:6. And though God commanded them in their march to Canaan to spare the Moabites, Deuteronomy 2:9,19, yet afterwards they proved unthankful, and insolent, and fierce enemies to God and his people, Numbers 22:2, Numbers 24:17,18 Jud 3:14, &c.; 1 Samuel 14:47, &c., and thereby provoked God to alter his course and carriage towards them. With a line, i. e. as with line, the particle as being oft understood, as Psalms 11:1, Psalms 22:6 45:1. The sense is, having conquered the land, he made an estimate of it, and, as it follows, distributed the towns and people into three parts. Casting them down to the ground, i. e. overthrowing their towns, and utterly destroying their people in, manner following. With two lines measured he to put to death; which severity was necessary for his own and his people's security, because they were numerous and potent, and bordering upon Canaan, and very vexatious and mischievous to the Israelites. And now that prophecy, Numbers 24:7, was accomplished.
Related Commentaries of 2 Samuel 8:2
2 Samuel 8:2
2 And he smote Moab, and measured them with a line, casting them down to the ground; even with two lines measured he to put to death, and with one full line to keep alive. And so the Moabites became David's servants, and brought gifts.