Jesus does a similar thing here in verse 27 as He did back in verse 21. He takes the law, which was the cultural standard of the day, and begins to redefine it. He begins in verse 27: "You have heard it said..." As I stated last week, the problem with the religious leaders of the day is that they had taken God's commands and made them about outward appearance rather than inward character. Jesus shows us that what we do is a direct reflection of our heart. The only way to walk in obedience to God is to have a heart for God.
In the same way that anger in the heart is a sin comparable to murder, lustful intent is a sin like adultery. Jesus calls His followers to fight against lust with every fiber in our body. Jesus even uses deliberate overstatement in order to emphasize the radicalness that should accompany obedience to Him. For example, "if your right eye causes you to sin, tear it out and throw it away." Or, "if your right hand causes you to sin, cut it off and throw it away."
Jesus shows us how high the stakes are. It is a matter of eternal life and death! Again, He is still pointing at the heart. What these verses are revealing is how truly fallen and sinful we really are. As Daniel Akin states, "We often reduce sin to what we do. Jesus makes it clear, however, that sin is rooted in who we are." We are more sinful than we realize. But when we have a heart for Christ, we will desire to take radical measures in order to guard our hearts and minds.
This is only possible through the gospel! It is the power of the gospel that frees our hearts and minds in order to pursue this kind of purity. We must look to how Jesus treats His Bride, the Church, as the ultimate model of how we are to love our spouses. We look to how Jesus treated women, with love and dignity, for the model of how men are to treat women (and vice versa). He is the ultimate example of a kingdom-minded person! May we all, as people shaped by the gospel, pursue this kind of purity.