But it came to pass when Nebuchadrezzar king of Babylon came up into the land that we said Come and But it came to pass, when Nebuchadrezzar king of Babylon came up into the land, that we said, Come, and let us go to Jerusalem for fear of the army of the Chaldeans, and for fear of the army of the Syrians: so we dwell at Jerusalem.
For fear of the army of the Chaldeans and ... of the Syrians - when Jehoiakim revolted from Nebuchadnezzar (2 Kings 24:1-2, and "the Lord sent against him bands of the Chaldeans and of the Syrians"). Necessity sets aside all other laws. This is the Rechabites' excuse for their seeming disobedience to Jonadab in temporarily settling in a city. Herein was seen the prescient wisdom of Jonadab's commands: they could at a moments notice migrate, having no land-possessions to tie them.