The word that came to Jeremiah concerning all the people of Judah in the fourth year of Jehoiakim the son of Josiah king of Judah, that was the first year of Nebuchadrezzar king of Babylon;
The message given to Jeremiah about all the people of Judah happened during Jehoiakim's fourth year as king, which was also when Nebuchadnezzar became the king of Babylon for the first time.