They say, etc.; as the margin of Authorized Version correctly states, the Hebrew simply has "saying." Various ingenious attempts have been made to explain this. Hitzig, for instance, followed by Dr. Payne Smith, thinks that "saying" may be an unusual equivalent for "that is to say," "for example," or the like; while the Vulgate and Rashi, followed by De Wette and Rosenmüller, assume an ellipsis, and render, "It is commonly said," or "I might say."
But far the most natural way is to suppose that "saying" is a fragment of the superscription of the prophecy, the remainder of which has been accidentally placed in Jeremiah 3:6, and that we should read, "And the word of the Lord came unto me in the days of Josiah the king, saying."
So J. D. Michaelis, Ewald, Graf, Naegelsbach. If a man put away his wife. The argument is founded on the law of Deuteronomy 24:1-4, which forbade an Israelite who had divorced his wife to take her again, if in the interval she had been married to another.
The Jews had broken a still more sacred tie, not once only, but repeatedly; they worshipped "gods many and lords many;" so that they had no longer any claim on Jehovah in virtue of his "covenant" with his people.
Shall he return, etc.? rather, Ought he to return? The force of the term is potential (comp. Authorized Version of Genesis 34:7, "which thing ought not to be done"). Shall not in the next clause is rather would not.
Yet return again to me. So Peshito, Targum, Vulgate, and the view may seem to be confirmed by the invitations in Deuteronomy 24:12, Deuteronomy 24:14, Deuteronomy 24:22. But as it is obviously inconsistent with the argument of the verse, and as the verb may equally well be the infinitive or the imperative, most recent commentators render, "And thinkest thou to return to me?"
(literally, and returning to me! implying that the very idea is inconceivable). Probably Jeremiah was aware that many of the Jews were dissatisfied with the religious condition of the nation (comp. verse 4).