The former promise would have been defective had not this clause been added; for it would not be enough for men to live as they please, and to have liberty promised them, except a regular order be established. It would, indeed, be better for us to be wild beasts, and to wander in forests, than to live without government and laws; for we know how furious are the passions of men. Unless, therefore, there be some restraint, the condition of wild beasts would be better and more desirable than ours. Liberty, then, would ever bring ruin with it, were it not bridled and connected with regular government. I therefore said that this verse was added, that the Jews might know that God cared for their welfare; for he promises that nothing would be wanting to them. It is then a true and real happiness, when not only liberty is granted to us, but also when God prescribes to us a certain rule and sets up good order, that there may be no confusion. Hence Jeremiah, after having promised a return to the people into their own country, and promised also that the yoke would be shaken off from their neck, makes this addition, that having served strangers they would be now under the government of God and of their own king. Now this subjection is better than all the ruling powers of the world; that is, when God is pleased to rule over us, and undertakes the care of our safety, and performs the office of a Governor. We hence see that the design of the Prophet was to comfort the faithful, not only with the promise of liberty, but also with this addition, that in order that nothing might be wanting to their complete happiness, God himself would rule over them. Serve, then, shall they their God The word king is added, because God designed that his people should be governed by a king, not that the king would sit in the place of God, but added as his minister. Now this was said a long time after the death of David; for David was dead many years before Jeremiah was born: nor did he live again in order that he might rule over the people; but the name of David is to be taken here for any one that might succeed him. Now, as God had made a covenant with David, and promised that there would be always one of his posterity to sit on his throne, hence the Prophet here, in mentioning David, refers to all the kings until Christ: and yet no one after that time succeeded him, for the kingdom was abolished before the death of Jeremiah; and when the people returned into their own country there was no regal power, for Zerubbabel obtained only a precarious dignity, and by degrees that royal progeny vanished away; and though there were seventy chosen from the seed of David, yet there was no scepter, no crown, no throne. It is therefore necessary to apply this prophecy to Christ; for the crown was broken and trodden under foot, as Ezekiel says, until the lawful king came. He intimated that there was no king to be for a long time, when he said, "Cast down, cast down, cast down the crown." (Ezekiel 21:27) He therefore commanded the name of a king to be abolished, together with all its symbols, and that not for a short time but for ages, even until he came forth who had a just right to the crown or the royal diadem. We hence see that this passage cannot be otherwise explained than by referring to Christ, and that he is called David, as the Jews were always wont to call him before Christ appeared in the world; for they called the Messiah, whom they expected, the Son of David. We now understand the meaning of the Prophet. But we may hence gather a very useful doctrine, even this, -- that nothing is better for us than to be in subjection to God; for our liberty would become that of wild beasts were God to allow us to live according to our own humor and inclinations. Liberty, then, will ever be destructive to us, until God undertakes the care of us, and prepares and forms us, that we may bear his yoke. Hence, when we obey God, we possess true and real happiness. When, therefore, we pray, let us learn not to separate these two things which ought necessarily to be joined together, even that God would deliver us from the tyranny of the ungodly, and also that he would himself rule over us. And this doctrine is suitable to our time: for if God were now only to break down the tyranny of the Pope and deliver his own people, and suffer them to wander here and there, so as to allow every one to follow his own will as his law, how dreadful would be the confusion! It is better that the devil should rule men under any sort of government, than that they should be set free without any law, without any restraint. Our time, indeed, sufficiently proves, that these two things have not, without reason, been joined together; that is, that God would become the liberator of his people, so as to shake off the yoke of miserable bondage and to break their chains, and also that he would be a king to govern his people. But we ought also carefully to notice what follows, -- that God would not otherwise govern his Church than by a king. He designed to give an instance, or a prelude, of this very thing under the Law, when he chose David and his posterity. But to us especially belongs this promise; for the Jews, through their ingratitude, did not taste of the fruit of this promise: God deprived them of this invaluable benefit, which they might justly and with certainty have expected. As the favor which they have lost has now been transferred to us, what Jeremiah teaches here, as I have said, properly belongs to us; that is, that God is not our king except we obey Christ, whom he has set over us, and by whom he would have us to be governed. Whosoever, then, boast that they willingly bear the yoke of God, and at the same time reject the yoke of Christ, are condemned by this very prophecy; for it is not God's will to rule uninterveniently, so to speak, his Church; but his will is that Christ, called here David, should be king; unless, indeed, we accuse Jeremiah of stating an untruth, we must apply the word David to the person of Christ. Since it is so, God then will not otherwise rule over us than by Christ, even to the end of the world; we must obey him and render him service. He adds, Whom I will raise up It was also the office and work of God to raise up Christ, according to what is said in the second Psalm, "I have anointed my King." We must always come to the fountain of God's mercy, if we would enjoy the blessings of Christ, according to what is said, "God so loved the world, that he gave his only begotten Son." We shall, indeed, find in Christ whatever is necessary for our salvation; but whence have we Christ, except from the infinite goodness of God? When he pitied us, he designed to save us by his only begotten Son. Salvation then is laid up for us in Christ, and is not to be sought anywhere else: but we ought, ever to remember that this salvation flows from the mercy of God, so that Christ is to be viewed as a testimony and a pledge of God's paternal favor towards us. This is the reason why the Prophet expressly adds, that God would raise up a king to rule over his people. It follows --

David their king - See Jeremiah 23:5-6; i. e., Messiah.

But they shall serve the Lord their God, and David their King - This must refer to the times of the Messiah and hence the Chaldee has, "They shall obey the Lord their God, וישת מאון למשיחה בר דוד veyishta meun limschicha bar David, and they shall obey the Messiah, the Son of David." This is a very remarkable version; and shows that it was a version, not according to the letter, but according to their doctrine and their expectation. David was long since dead; and none of his descendants ever reigned over them after the Babylonish captivity, nor have they since been a regal nation. Zerubbabel, under the Persians, and the Asmoneans, can be no exception to this. They have been no nation since; they are no nation now; and it is only in the latter days that they can expect to be a nation, and that must be a Christian nation.
Christ is promised under the name of his progenitor, David, Isaiah 55:3, Isaiah 55:4; Ezekiel 34:23, Ezekiel 34:24; Ezekiel 37:24, Ezekiel 37:25; Hosea 3:5.

But they shall serve the LORD their God, and (g) David their king, whom I will raise up to them.
(g) That is, Messiah who would come of the stock of David according to the flesh and would be the true pastor, (Ezekiel 34:23) who is set forth and his kingdom would be everlasting in the person of David, (Hosea 3:5).

But they shall serve the Lord their God,.... And him only, in a spiritual manner, in righteousness and true holiness, with reverence and godly fear; having respect to all his precepts and ordinances, and every branch of religious worship; joining themselves to Gospel churches, and worshipping along with them, before them, and in the midst of them; see Revelation 3:9;
and David their king; not literally, who shall be raised up from the dead, and reign over them, which Kimchi supposes possible, though he does not assert it; nor his successors called by his name, as the kings of Egypt were called Pharaohs and Ptolemies, and the Roman emperors Caesars, of which we have no instance; nor were there any kings of David's line upon the throne of Israel after the Babylonish captivity, until the Messiah came, and who is the Person here meant; and so the Targum paraphrases it,
"and they shall hearken to, or obey, Messiah the son of David their king;''
and Kimchi owns that it may be interpreted of Messiah the son of David, whose name is called David, as it is in many prophecies, Ezekiel 34:23; and this prophecy is understood of the Messiah by several Jewish writers (s); and in the Talmud (t) it is said,
"the holy blessed God will raise up unto thee another David; as it is said, "and they shall serve the Lord their God, and David their king, whom I will raise up unto them"; it is not said, "he hath raised up", but "I will raise up";''
and Christ is called David, not only because he is his son, but because he is his antitype. David was a type of Christ in his birth and parentage; the son of Jesse, born of mean parents, and at Bethlehem; in his outward form, ruddy and beautiful; in his inward character, a man of holiness, wisdom, and courage; in his offices of shepherd, prophet, and king; in his afflictions and sorrows, and in his wars and victories. The same Person is here meant as in the former clause, "the Lord their God"; since it is Jehovah that is here speaking; and he does not say "they shall serve me", but "the Lord their God"; and since the same service is to be yielded to David as to the Lord their God; and who is, in his divine nature, the Lord God, and so the object of all religious worship and service; and, in his human nature, of the seed of David; and by office a King, appointed by his Father, and owned by his people, as King of saints; so the words may be rendered, "they shall serve the Lord their God, even David their King"; see Titus 2:13;
whom I will raise up unto them; which is said of him in all his offices, Jeremiah 23:5; and is expressive of his constitution as Mediator; and includes the Father's pitching upon him, appointing him, calling him, fitting and qualifying him, and sending him in the fulness of time, under this character, as a Mediator, Redeemer, and Saviour; all which was for the good of his people; as a favour to them, for their profit and advantage: his incarnation is for them; his obedience, sufferings, and death; his righteousness, and the salvation he wrought out; he is raised up, and sent to them to bless them, with all spiritual blessings that are in him, Acts 3:26.
(s) R. Albo in Sepher lkkarim, l. 2. c. 28. Abarbinel in loc. & in Mashmiah Jeshuab, fol. 35. 4. (t) T. Bab. Sanhedrin, fol. 98. 2.

Instead of serving strangers (Jeremiah 30:8), they shall serve the Lord, their rightful King in the theocracy (Ezekiel 21:27).
David, their king--No king of David's seed has held the scepter since the captivity; for Zerubbabel, though of David's line, never claimed the title of "king." The Son of David, Messiah, must therefore be meant; so the Targum (compare Isaiah 55:3-4; Ezekiel 34:23-24; Ezekiel 37:24; Hosea 3:5; Romans 11:25-32). He was appointed to the throne of David (Isaiah 9:7; Luke 1:32). He is here joined with Jehovah as claiming equal allegiance. God is our "King," only when we are subject to Christ; God rules us not immediately, but through His Son (John 5:22-23, John 5:27).
raise up--applied to the judges whom God raised up as deliverers of Israel out of the hand of its oppressors (Judges 2:16; Judges 3:9). So Christ was raised up as the antitypical Deliverer (Psalm 2:6; Luke 1:69; Acts 2:30; Acts 13:23).

Then Israel will no longer serve strangers, i.e., foreign rulers who are heathens, but their God Jahveh, and David the king who will be raised up to them, i.e., the Messiah, the righteous sprout that Jahveh will raise up to David; cf. Jeremiah 23:5. The designation of this sprout as "David their king," i.e., the king of the Israelites, points us back to Hosea 3:5.

But - Either this must be understood of the kingdom of Christ, under which the Jews that received him were made spiritually free: or there is a time yet to come, when this ancient people of God shall be restored to a farther civil liberty than they have enjoyed ever since the captivity of Babylon.