Jeremiah 3:1 finds its antecedent in Deuteronomy 24:1–4, which “forbade the remarriage of a man with his divorced wife, even if her second husband had died or divorced her. The purpose of the law was to curb the husband’s arbitrary use of his right to divorce his wife.”[1] 
In Jeremiah chapter 3, the prophet returns to the subject of marriage and infidelity. He uses a common custom in Israel to make his point. The custom was that when a couple divorces and the wife marries another man she has crossed the Rubicon, so to speak. She has burned her last bridge and her husband can never and will never want her back. The “law” as such has harsh demands on people. This verse says, “If a man divorces his wife and she goes from him and becomes another man’s wife, will he return to her? Would not that land be greatly polluted? You have played the whore with many lovers; and would you return to me? declares the LORD.”
Yet Jeremiah as well as Hosea and the other prophets are still calling God’s unfaithful spouse to turn away from her many lovers and to come home where they will be forgiven and loved unconditionally. Even under the law, God operated in His relationship with His people under the law of love. In Matthew 18, Jesus tells of the master who forgave a huge debt of one of his servants who turned around and applied the harsh realities of the law to one who owed him. Jesus clearly understood the difference between living under the law and living under love. God knew it too and we see that even in the Old Testament, “The Covenant of Law.”
Feinberg observes, “We must never forget that God, as he wills, exercises grace beyond the law. Ruth was a Moabitess and was excluded from Israel (cf. Deut 23:3); how then does she become the ancestress of David and of the Lord Jesus? God operated by grace beyond the law. So God was ready to forgive Judah in spite of all her past failures.”[2] That’s great news for you and me! No matter what we’ve done, how long we’ve done it, with whom we’ve done it there is always hope that the God of unconditional love will still take me back! One commentary suggests the thinking of the prodigal son, “The turning point comes when this willfully lost young man ‘comes to himself,’ which simply suggests that he makes a wise choice. He says, ‘This is stupid. I don’t need to live like this. I have a home and a father. Maybe he will take me back as a servant.’”[3] As a servant? Are you kidding me? He has the family ring, the robe and the fatted calf ready to celebrate your return!
[1] Charles L. Feinberg, “Jeremiah,” in The Expositor’s Bible Commentary: Isaiah, Jeremiah, Lamentations, Ezekiel, ed. Frank E. Gaebelein, vol. 6 (Grand Rapids, MI: Zondervan Publishing House, 1986), 397.
[2] Charles L. Feinberg, “Jeremiah,” in The Expositor’s Bible Commentary: Isaiah, Jeremiah, Lamentations, Ezekiel, ed. Frank E. Gaebelein, vol. 6 (Grand Rapids, MI: Zondervan Publishing House, 1986), 397.
[3] Bruce Larson and Lloyd J. Ogilvie, Luke, vol. 26, The Preacher’s Commentary Series (Nashville, TN: Thomas Nelson Inc, 1983), 236–237.