Does God's divorce of Israel prove that we can divorce?

As a fundamental principle of interpretation, we hold that the Bible never contradicts itself, having been authorized by the Creator Himself. So all Scripture is consistent and in agreement with itself. So if we find Scripture that appears to contradict Jesus' teaching on divorce and remarriage, we proceed on the expectation that these two passages are actually in agreement, and therefore our understanding is lacking in some respect. 

With that background, Jesus' words are utterly clear on divorce and remarriage, so we must seek an understanding of God's actions and words in the Old Testament which are consistent with Jesus' words in the New Testament, since the two passages were written by the same Lord. In the case of Jeremiah 3:1, the Lord says:

Jer. 3:1 God says, “If a husband divorces his wife 
    And she goes from him 
    And belongs to another man, 
    Will he still return to her? 
    Will not that land be completely polluted? 
    But you are a harlot with many lovers; 
    Yet you turn to Me,” declares the LORD.

The Lord uses the principle of marriage to teach Israel a lesson about her unfaithfulness. He reminds Israel that when man divorces his wife and sends her to another husband, the woman may never return to her first husband. When she remarried, she committed adultery (as Jesus says), so if she returned to the first husband, then he would likewise be committing adultery with her (since she is now married to another man).

The Lord uses the illustration of marriage to explain to Israel how unreasonable their actions have been toward the Lord. They are acting unfaithfully against the Lord in a spiritual relationship much like a woman who cheats on her husband. And then having played the harlot with idols, Israel expected the Lord to welcome her back time and time again. 

The Lord uses the example of marriage to illustrate how unreasonable Israel's expectations were, but it is only an illustration. The Lord and Israel are not literally husband and wife. We can see that the Lord uses this comparison metaphorically in many areas of the Bible:

Is. 62:5  For as a young man marries a virgin, 
    So your sons will marry you; 
    And as the bridegroom rejoices over the bride, 
    So your God will rejoice over you.

As we see in this verse from Isaiah, marriage is merely an illustration of Israel's relationship to the Lord, not a literal description. So the proper interpretation of Jeremiah 3 is that the Lord will not forsake His covenant to Israel, showing surpassing grace toward His people. The Lord will one day welcome Israel's return into the covenant relationship He established because it is not a literal marriage, and therefore we cannot use Jeremiah 3 as a reference when determining the rules for human marriage. 

Moreover, the Lord's purpose in using marriage to illustrate His relationship with Israel in Jeremiah 3 would be completely negated if we believe that a wife could return to her husband after having remarried. If that were permissible, then the Lord's concern for Israel in Jeremiah 3 would be pointless. The Lord is charging Israel with an an unreasonable expectation because they seek to do something that was unlawful in marriage (i.e., to expect a husband to reunite with a woman who has already remarried).So the teaching of Jeremiah 3 doesn't contradict the teaching of Jesus; rather, it affirms Jesus' teaching. 

Secondly in Ezra 10, Israel is told to put away foreign wives, which were taken in disobedience to the Lord. These marriages were unlawful because they were in violation of the Law of Moses, which commanded the sons of Israel to abstain from marrying foreign wives. Since the Jewish men married against the Law, their marriages were unlawful. 

A Christian is not under the Law of Moses, so there are no "unlawful" marriages. Every marriage is lawful, though a marriage to one who is divorced is ALSO an act of adultery. Nowhere in the Bible are we told that an act of adultery invalidates a marriage. On the contrary, Paul tells us that illicit sexual acts result in a one-flesh relationship:

1Cor. 6:14 Now God has not only raised the Lord, but will also raise us up through His power.
1Cor. 6:15 Do you not know that your bodies are members of Christ? Shall I then take away the members of Christ and make them members of a prostitute? May it never be!
1Cor. 6:16 Or do you not know that the one who joins himself to a prostitute is one body with her? For He says, “THE TWO SHALL BECOME ONE FLESH.”
1Cor. 6:17 But the one who joins himself to the Lord is one spirit with Him.

So we cannot use the moment in Ezra 10 to establish our theology of Christian marriage. The circumstances of Ezra are uniquely applicable to Jewish men living under the Law marrying non-Jewish women. Therefore, Ezra's command to Israel is not relevant to how we conduct ourselves in marriage today.

Finally, in the Gospels John the Baptist is imprisoned for criticizing Herod Antipas on his marriage to Herodias:

Matt. 14:1 At that time Herod the tetrarch heard the news about Jesus,
Matt. 14:2 and said to his servants, “This is John the Baptist; he has risen from the dead, and that is why miraculous powers are at work in him.”
Matt. 14:3 For when Herod had John arrested, he bound him and put him in prison because of Herodias, the wife of his brother Philip.
Matt. 14:4 For John had been saying to him, “It is not lawful for you to have her.”
Matt. 14:5 Although Herod wanted to put him to death, he feared the crowd, because they regarded John as a prophet.

John's complaint that the king's marriage was unlawful did not stem from his adultery, it referred to the incestuousness nature of the relationship. In marrying his brother's wife while his brother was still alive, he was technically marrying his sister, according to the Law in Leviticus 18:16 and 18:20-21. An incestuous marriage is unlawful and therefore invalid, but again a marriage formed through an act of adultery is not invalid. 

Once again, the teaching of Scripture is not in contradiction, and we urge you to obey Jesus' words concerning marriage. Remain faithful to your current wife and let that be the testimony for the remainder of your earthly life. 

Scripture quotations taken from the (NASB®) New American Standard Bible®, Copyright © 1995, 2020 by The Lockman Foundation. Used by permission. All rights reserved. www.lockman.org