Adam Clarke on Jeremiah 42:22

Now therefore know certainly - As ye have determined to disobey, God has determined to punish. Ye may now follow the full bent of your wicked devices, and I will follow the requisitions of my justice. Ye shall die by the sword, by the pestilence, and by the famine, in the place whither ye desire to go to sojourn. Thus was their doom sealed.

With such dispositions and with such rebellion of heart, it is strange that they should put themselves to any trouble to inquire of the Lord relative to their future operations. They did not intend to obey; but as a matter of curiosity they would inquire to hear what the prophet might say; and if according to their own inclination, they would obey.