Charles Ellicott Commentary Jeremiah 30:9

"but they shall serve Jehovah their God, and David their king, whom I will raise up unto them." — Jeremiah 30:9 (ASV)

David their king ... —The name of the old hero-king appears as that of the new representative of the house who is to restore the kingdom. There is to be a second David for Israel, a true king answering to the ideal which he imperfectly represented. Zerubbabel, in whom some interpreters have seen the fulfilment of Jeremiah’s words, was, in his measure, another partial representative of such a king (Haggai 2:21–23). The same mode of speech appears in Hosea 3:5 and Isaiah 55:4, and was probably deliberately reproduced by Jeremiah.