Jeremiah 42:6

The preceding words are a perfect oath, the form of which lies in a calling of God to witness the sincerity of the heart of those that swear, for a security to those to whom the oath is given, which also includeth a secret challenging God to take vengeance upon the persons that give that security, if they should not do accordingly as they promise; which speaketh the atheism of the heart of the false swearer; for did a man believe that there is a God, and that the Divine Being is infinite in power, and a true and faithful witness, it were impossible that he should challenge him to be revenged on him-for not doing what he never seriously intends to do, which was the case of these wicked men. The thing they promise is a perfect obedience to God's will, whether grateful or ungrateful to them; and they further declare a conviction, that if they did it, it should be well with them, according to that, Deuteronomy 5:29; which showeth the mighty power of lusts in unregenerate hearts, and the mighty operations of the evil spirit in the children of disobedience, Ephesians 2:2; that although they be convinced that if they did obey the voice of God it would be well with them, yet they will not do it in things which they have a power to do.