Charles Ellicott Commentary Jeremiah 36:1

"And it came to pass in the fourth year of Jehoiakim the son of Josiah, king of Judah, that this word came unto Jeremiah from Jehovah, saying," — Jeremiah 36:1 (ASV)

The fourth year of Jehoiakim ... —The prophetic message that follows is brought by the date thus given into close contact with Jeremiah 25:0, and it is a reasonable inference that we have in that chapter the substance of part, at least, of what was written by Baruch from the prophet’s dictation in Jeremiah 36:4. The contents exactly agree with the description of the prophecy given here in Jeremiah 36:2.