Last week we looked at the subject of anger in Matthew 5:21-26. The main idea was that true righteousness is not characterized by outward behavior but a pure heart. Therefore, simply avoiding murder isn’t a defining mark of righteousness, but cleansing our hearts from underlying anger and putting on love, forgiveness, and compassion is. This is the kind of righteousness that Jesus is calling us to. It is the righteousness that the Spirit will create in the members of God’s kingdom.
In this section of the Sermon on the Mount, Jesus describes what true righteousness looks like in the context of personal relationships. To do that, he quotes the law and shows where the religious leaders only obey the tradition at the surface level. But he also reveals how the principle should be obeyed at the heart level, where almost all of us stand guilty. This is exactly what he did with murder, revealing that the heart behind murder is anger. Thus, anyone who is angry is, in some sense, guilty of murder. This revelation is painful, but we must remember that the righteousness described in the SM is not a prerequisite for salvation. We are saved by Jesus, who has paid the penalty for our unrighteousness and has given us his righteousness. He has also cleansed our hearts and given us his Spirit, by whom he will flesh out the righteousness that the SM speaks of in our lives.
In Matthew 5:27-32, Jesus continues his discourse on relationships by addressing the relationship of marriage. What does true righteousness look like in the relationship between husband and wife? Jesus points to two aspects of the law to answer that question: adultery and divorce.
“You have heard it said, ‘You shall not commit adultery’ but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart” (5:28). Just like he does with murder, Jesus takes the obvious, public (once it is brought to light) sin and drives it to the heart level. In essence, he says, “You think you are righteous if you abstain from adultery, but you are actually guilty of adultery by simply lusting after another woman.”
Jesus’ heart-checks should have been met with the religious leaders’ recognition of their inability to keep the law perfectly and their subsequent need of a Savior who can keep it perfectly. However, they remained content to keep the surface-level aspects of the law while neglecting the weightier matters of the law (Matt. 23:23).
Jesus continues this idea in his comments on divorce, “Now it was said, ‘whoever sends his wife away is to give her a certificate of divorce,’ but I say to you that everyone who divorces his wife, except for the reason of sexual immorality, makes her commit adultery,” (Matt. 5:31-32). The religious leaders, by mis-applying Deuteronomy 24:1, had taken a phrase from the law and turned it into a convenient way for husbands to divorce their wives for any reason. They would divorce their wives, marry another woman, and have many intimate relationships without “actually” committing adultery.
Jesus is saying, “If you divorce your wife for sinful and selfish reasons, you make her commit adultery. Thus, just like with lust, you are guilty of adultery.” Why are they guilty of adultery? Because they are violating marriage vows, breaking trust, and desecrating marital purity if they discard their spouse for their own selfish reasons- chief among them being lust after another woman. And yet, the religious leaders, the “keepers of the Law,” believed that they could do all of these things and remain righteous and as long as they did not legally have adultery or divorce their wives without a certificate.
Jesus is saying, “it will not be so in my kingdom.” The righteousness that characterizes the members of the New Covenant far surpasses the righteousness of the scribes and Pharisees (Matt. 5:20). So, what does that righteousness look like in the context of marriage relationships?
It looks like searching your heart and being willing to remove anything from your life that could even possibly lead you to lust (v. 29-31). Cut the cable. Delete social media apps. Workout at home. Make war with the thoughts in your head. Be just as defensive against lust as adultery itself. “Guard your heart” (Proverbs 4:23).
But this righteousness is not only defensive, it is offensive. Kingdom-minded spouses don’t simply avoid lust and/or adultery for the sake of their marriage, they actively pursue loving one another. “Husbands, love your wives, as Christ loved the church and gave himself up for her” (Ephesians 5:25, emphasis mine). This applies to wives as well, who are called to love their husbands with sacrificial love and exhibit the character of Christ in their marriage (Ephesians 5:22-24; 1 Peter 3:1).
This is the kind of righteousness that far surpasses that of the scribes and Pharisees (Matt. 5:20). It proceeds from a heart that has been cleansed from sin, reconciled to God, and filled with the Holy Spirit.
Let us hunger and thirst for this righteousness, seeking to live it out in our marriage relationships, and we will be satisfied! (Matt. 5:6).
 They made the phrase “some indecency” in Deut. 24:1 “as wide as the ocean.” They even developed list of indecencies that were permissible for divorce- including burnt toast!
Douglas Sean O’Donnell, Matthew (Crossway: Wheatin, IL, 2013), 139.