John Calvin on Jeremiah 42:3

They came then, as it has been stated, as though they were ready to obey; and then they professed humility, because they did not wish to do anything rashly, but only to follow where God called them. Had they spoken from the heart, it would have been a rare virtue thus to-have fled in perplexities to God, and to have allowed themselves to be ruled by his word; but we shall see that it was all a pre-tence. We have then here set before us the hypocrisy of that people, so that we may learn that whenever we ask what pleases God, we should bring a pure and sincere heart, so that nothing may prevent or hinder us immediately to embrace whatever God may command us. But their hypocrisy is discovered to have been still baser, when the Prophet adds,

Jeremiah 42:4

4. Then Jeremiah the prophet said unto them, I have heard you; behold, I will pray unto the LORD your God according to your words; and it shall come to pass, that whatsoever thing the LORD shall answer you, I will declare it unto you; I will keep nothing back from you.

4. Et dixit illis Jeremias Propheta, Audivi, ecce ego orabo Jehovam Deum vestrum secundum sermones vestros, et erit quemcunque sermonem responderit Jehova vobis, annuntiabo vobis, non celabo a vobis quicquam.