Adam Clarke on Jeremiah 33:22

So will I multiply the seed of David - This must be understood of the spiritual David, Jesus Christ, and his progeny, genuine Christians. The two families which God chose for the priesthood, that of Aaron and Phinehas, or, on its being taken away from him, that of Ithamar, 1Sam 2:35, are both extinct. Nor has the office of high priest, or priest of any kind offering sacrifice, been exercised among the Jews for nearly eighteen hundred years; therefore what is said here of the priesthood must refer to the spiritual priesthood, at the head of which is Jesus Christ.