Jeremiah 21

Jeremiah 21:2 Nebuchadrezzar king of Babylon maketh war against us
“Although Nebuchadnezzar did not come up to siege Jerusalem until the ninth year of Zedekiah's reign (38:1), there had probably been a continual threat that he would do so; therefore, the date this prophecy was given is not known. The fact that there was a condition of repentance implies that the prophecy was given earlier than the ninth year of Zedekiah's reign. Jeremiah's strong proclamation of the fall of Jerusalem was undoubtedly not what Zedekiah had hoped for.” (Monte S. Nyman, The Words of Jeremiah [Salt Lake City: Bookcraft, 1982], 68)
Jeremiah 21:2 Enquire, I pray thee, of the Lord for us… if so be that the Lord will deal with us according to all his wondrous works
Kings contemplating battles would often inquire of the prophets. 
  • As Moses and the Israelites closed in on the land of Canaan, they destroyed every army that came against them to battle. Balak, the king of Moab, sent messengers to Balaam the prophet, “curse me this people… that I may drive them out of the land” (Numb. 22:6)
  • Wicked Ahab of Israel sought military advice of the prophets, “Shall I go up against Ramoth-gilead to battle or should I forbear?” (1 Kgs. 22:6)
  • Elisha advised the king of Israel as to the location of the Syrian camp exasperating the Syrian king.  His servant declared to him, “Elisha, the prophet that is in Israel, telleth the king of Israel the words that thou speakest in thy bedchamber” (2 Kgs. 6:12)
  • Moroni sent messengers to Alma that he might know where “the armies of the Nephites should go to defend themselves against the Lamanites” (Alma 43:23)
What a great advantage to have a prophet to ask in times of war!  So Zedekiah does the right thing, he sends messengers to the Lord’s prophet for advice.  Usually, historically, the answer has been, “go up against your enemies and I, the Lord, will deliver them into your hands.”  This is the message that Zedekiah wants to hear, but that is not what he gets.  Balak didn’t get the message he wanted from Balaam.  Ahab didn’t get what he wanted from Miciah declaring, “I hate him; for he doth not prophesy good concerning me, but evil.” (1 Kgs. 22:8) 
Zedekiah started with the right idea but he couldn’t finish what he started.  What good is the faith to ask the prophet for advice if you don’t have the courage to follow his counsel?  A modern day corollary applies to us as well.  What good is it to ask God for advice if we don’t have the courage to follow the counsel He gives us?  What good does it do to discuss a problem with the bishop if we are not willing to follow his counsel?  Do we want to be like Zedekiah, Balak, and Ahab—too stubborn to follow the counsel of the Lord’s ordained servants?
Jeremiah 21:5 I myself will fight against you with an outstretched hand and a strong arm
“King Zedekiah sent two messengers, Pashur and Zephaniah, to Jeremiah with the request that he inquire of the Lord on behalf of the king and all of Judah ‘if so be that the Lord will deal with us according to all his wondrous works, that he may go up from us’ (Jer. 21:2). The phrase ‘wondrous works’ (Hebrew, niple'ot) is used throughout the Old Testament to refer to the ‘mighty acts’ that the Lord performed in the deliverance of Israel from Egypt.  Zedekiah hoped that the Lord God of Israel would deliver his people now through his miraculous power as he had at the time of Moses from the Egyptians and most recently from the Assyrians at the time of Hezekiah (2 Kgs. 18-19; Isa. 36-37). The Lord's reply was grim. Not only would he not aid Judah in her defense (Jer. 21:4) but, he said, ‘I myself will fight against you with an outstretched hand and with a strong arm, even in anger, and in fury, and in great wrath’ (Jer. 21:5). The phrase ‘mighty hand and a stretched out arm’ is another key formula used in reference to the Lord's strength in defeating Pharaoh's army, whose destruction is portrayed as a military encounter during the Exodus (Deut. 4:34; 5:15; 7:19; 11:2; 26:8).  In Jeremiah, though, the adjectives of the formula are switched, ‘outstretched hand and strong arm’ indicating the reversal that has come about through Judah's transgressions. Whereas before the Lord fought for Israel against her enemies, now the Lord will join the enemy and fight against his people.  In addition to this grim tiding, the Lord said through Jeremiah: ‘He that abideth in this city shall die by the sword, and by the famine, and by the pestilence: but he that goeth out, and falleth to the Chaldeans that besiege you, he shall live, and his life shall be unto him for a prey’ (Jer. 21:9). The only chance for survival is surrender, a message for which Jeremiah would be branded a traitor (Jer. 38:2-4).” (Studies in Scripture, Vol. 4: 1 Kings to Malachi [Salt Lake City: Deseret Book Co., 1993], 237 - 238)
“I myself will fight against you.”  These are words the Lord had never before told his people.  When the Israelites came out of Egypt, the Lord promised, “Fear ye not, stand still, and see the salvation of the Lord… The Lord shall fight for you” (Ex. 14:13-14).  This had been the pattern for generations (Deut. 28:7; Josh. 10:14; 2 Chr. 20:15; Ps 35:1).  Even in the latter-days, the same promise has been given, “I do not require at their hands to fight the battles of Zion; for, as I said in a former commandment, even so will I fulfil—I will fight your battles” (D&C 105:14, italics added). The Jews were used to the Lord wielding his mighty sword in times of battle, but He was always fighting for them not against them!
Jeremiah 21:8  Behold, I set before you the way of life, and the way of death
Joseph B. Wirthlin
The Lord has left no doubt in defining His side and where the Saints should be in their thoughts, words, actions, and practices. We have His counsel in the scriptures and in the words of the prophets. To ancient Israel, the Lord said through Moses: “I have set before thee this day life and good, and death and evil.” (Deut. 30:15.) The Lord counseled His prophet Jeremiah to instruct the people: “Behold, I set before you the way of life, and the way of death.” (Jer. 21: 8.) That is the contrast; that is the choice. Either we are on the Lord’s side of the line or on the side of the adversary. Nephi declared, [we] “are free to act for [ourselves]—to choose the way of everlasting death or the way of eternal life.” (2 Ne. 10:23.) Yes, “men are free according to the flesh; and all things are given them which are expedient unto man. And they are free to choose liberty and eternal life, through the great Mediator of all men, or to choose captivity and death, according to the captivity and power of the devil; for he seeketh that all men might be miserable like unto himself.” (2 Ne. 2:27.) (“The Lord’s Side,” Ensign, Mar. 1993, 69)