John Calvin on Jeremiah 33:18

As to the priesthood, the same difficulty might be raised, for we know that the priesthood became corrupted; nay, that for the most part the priests not only became degenerate, but altogether sacrilegious. Hence the sacerdotal name itself became nothing else but a base and wicked profanation of all sacred things. But it was God’s purpose in this manner to shew that another priest was to be expected, and that men were not to look on figures and types, but were to raise their thoughts higher, even to him who was to be the only true Mediator to reconcile God to men.

By saying, who may kindle a burnt-offering, etc., he specifies certain things, or some parts of the priest’s office, because the Prophets accommodated their discourses to men of their own age and time, and described the kingdom and priesthood of Christ under those external symbols, which were then in use. It is hence proper to take the ceremonies of the Law as denoting the reality, or what they signified. For Christ offered no calves, nor any incense, but fulfilled all these things which were then set forth to the people under symbols. And he speaks of burning, or perfuming the oblation, מנחה, meneche, for though the oblation remained entire, there was yet a perfuming made by frankincense, and a small portion of the flour was burnt. It is then a mode of speaking, when a part is stated for the whole. It now follows —

Jeremiah 33:19-21

19. And the word of the LORD came unto Jeremiah, saying,

19. Et fuit sermo Jehovae ad Jeremiam, dicendo,

20. Thus saith the LORD; If ye can break my covenant of the day, and my covenant of the night, and that there should not be day and night in their season;

20. Sic dicit Jehova, Si irritum feceritis foedus meum diei et foedus meum noctis, ut non sint dies et nox suis temporibus;

21 Then may also my covenant be broken with David my servant, that he should not have a son to reign upon his throne; and with the Levites the priests, my ministers.

21. Etiam foedus meum abolebitur (hoc est, irritum fiet) cum Davide servo meo, ut non sit ei filius, qui regnet supra solium ejus et cum Levitis sacerdotibus ministris meis.