The Prophet here encourages the Chaldeans to severity, so as to make no end until they destroyed that nation. We have said that the prophets assumed different characters, so that what they said might be more impressive. The Chaldeans were not indeed the disciples of Jeremiah; nor was this exhortation intended for them, but that the Israelites might know that what they heard from the mouth of Jeremiah was certain. He then turns to address the Chaldeans; as he before spoke to any who might be present, "Give wings to Moab;" so now another apostrophe follows, Cursed, etc., -- to whom does he speak? to the Chaldeans; and yet the Prophet did not address them as though he could effect anything; but, as I have said, he had a regard to the Jews. This passage has been very absurdly explained, and it is commonly quoted as though the Prophet had said, that special care ought to be taken by us, not to omit anything of what God commands. But they thus misrepresent the meaning. We ought therefore to bear in mind what I have already said, that these words are addressed to the Chaldeans, as though he had said, "Spare not, but shed blood, and let no humanity move you, for it is the work of God; God has armed you, that ye might fully execute his judgment and spare no blood: ye shall then be accursed, except ye execute his vengeance." It is not indeed a common mode of speaking; but as to the subject and the meaning there is no ambiguity. It is the same thing as though he had said, "Go on courageously, and boldly execute God's vengeance, inasmuch as punishment has been denounced on them." As when soldiers idly delay, the leader when present not only exhorts them but also urges them on with reproofs and threatenings, in order to rouse their alacrity; so the Prophet here shews that God, as though present with the Chaldeans, would chide their sloth, "Why do ye give over? cursed is every one who will not shed blood, and who will not destroy them from the least to the greatest." But the whole import of the passage is found in the expression, that the destruction of that ungodly nation was the work of Jehovah; as if he had said, "Though the Chaldeans shall lay waste the land of Moab, and shall do this, not in order to obey God, but from avarice and ambition, yet it will be the work of God; for God has hired the Chaldeans for this end, that they might destroy the Moabites, though they may think of no such thing." It follows, --

Deceitfully - Better as in the margin.

Cursed be he that doeth the work of the Lord deceitfully - Moab is doomed to destruction, and the Lord pronounces a curse on their enemies if they do not proceed to utter extirpation. God is the Author of life, and has a sovereign right to dispose of it as he pleases; and these had forfeited theirs long ago by their idolatry and other crimes.

(h) Cursed [be] he that doeth the work of the LORD deceitfully, and cursed [be] he that keepeth back his sword from blood.
(h) He shows that God would punish the Chaldeans if they did not destroy the Egyptians, and that with a courage, and calls this executing of his vengeance against his enemies, his work though the Chaldeans sought another end, (Isaiah 10:11).

Cursed be he that doeth the work of the Lord deceitfully,.... Which is said with respect to the Chaldeans, who were enjoined to destroy the Moabites; which is called the work of the Lord, because he had given them a commission to do it; and which was to be done by them, not by halves, or in a remiss and negligent manner, but fully and faithfully; they were not to spare them, as Saul did the Amalekites, and Ahab Benhadad. This is a general rule, which may be applied to all divine work and service; every man has work to do for God; some in a more public, others in a more private way; all should be done in uprightness and sincerity, with all faithfulness and integrity: it is done deceitfully when men play the hypocrite; and negligently when they are backward to it, lukewarm in it, and infrequent in the performance of it; which brings upon them the curse of God; and which is not a curse causeless, but a legal one; and is no other than the wrath of God in strict justice:
and cursed be he that keepeth back his sword from blood; from shedding the blood of the Moabites, when God had given command to do it. The curse is repeated, as Kimchi observes, to confirm the matter, that it might be most assuredly expected; since it would certainly come, if the Lord's work was not done aright.

work of . . . Lord--the divinely appointed utter devastation of Moab. To represent how entirely this is God's will, a curse is pronounced on the Chaldeans, the instrument, if they do it negligently (Margin) or by halves (Judges 5:23); compare Saul's sin as to Amalek (1-Samuel 15:3, 1-Samuel 15:9), and Ahab's as to Syria (1-Kings 20:42).