Sermon on the Mount: Lust and Purity

Sermon on the Mount: Lust and Purity

Matthew 5: 27-32

Sex is like fire. In the fireplace it is good…Outside of the fireplace it burns the house down.– Ray Ortlund

As they did with the commandment to not murder, there were those (particularly the Pharisees and scribes) in Jesus’ day who reduced the commandment to not commit adultery to the very particular act of infidelity within the narrowly defined boundaries of marriage. By His teaching, Jesus showed them how the Law was actually asking for a far greater righteousness.

Marriage and Sex are Good Gifts from God

One of the mistakes we can make in talking about sex in the Church is to only speak about the forbidden aspects of it, rather than rightly extolling the beauty and blessing of it within marriage. Consider the following Biblical teaching on marriage and sex:

  • Genesis 2:18-24 and 1 Corinthians 7:3-5, which extol sex as an expression of the one flesh nature of the marriage union between a husband and his wife, who covenant to give themselves to one another for each other’s good and pleasure.
  • Proverbs 5:15-20, which illustrates the value of sex within marriage as something to be cherished and kept pure by comparing male and female sexuality to sources of water (cisterns, wells, streams, and fountains).
  • Leviticus 20:10; Deuteronomy 22:22; and Hebrews 13:4, which speak of God’s judgment upon those who defile the marriage bed. In Old Testament Israel the punishment for adultery was death, the same as that for murder. The severity of the judgment displays the value of marriage in the Lord’s sight, and the necessity of keeping the intimacy pure between husband and wife. That which God has joined together, no one should tear apart (Matthew 19:6).

The Misuse of Sex Begins in the Heart

Adultery does not just happen to someone. Rather, as Jesus pointed out, it is birthed from a heart of lustful intent. He rightly showed the self-righteous Pharisees that all have sinned sexually and fallen short of the glory of God. It is with pride and an air of superiority that one looks at another with lustful intent, selfishly objectifying that person and turning her into a means for one’s own gratification. Such objectification demeans her worth as someone created in the image of God whose chief end is to glorify Him, not to gratify another’s sexual desires. Jesus was showing His listeners that though the likes of the Pharisees congratulated themselves for their outward righteousness by not technically committing adultery in the legal sense, He knew that the story of their hearts was a different matter.

The Devaluing of Marriage and Sex

Jesus continued to show them their hypocrisy when he taught briefly about divorce. He used what was likely a Pharisaical misquoting of Deuteronomy 24:1-4 when He said, “Whoever divorces his wife, let him give her a certificate of divorce,” (v. 31; see also Matt. 19:1-9). The allowance for divorce for reasons of “some indecency” (Deut. 24:1) had come under a very liberal interpretation and men were known to write their wives a certificate of divorce for something as trivial as burning the evening meal. Once legally divorced they self-righteously believed themselves free of any guilt and thus able to remarry. But Jesus said that in divorcing her without just cause they committed adultery and caused their wives to also commit adultery.

Rather than valuing marriage and cherishing their wives the men were casting them off and, in the process, devaluing God’s good gifts of marriage and sex. (For more detail on this particular subject, see Jim Newheiser’s book, Marriage, Divorce, and Remarriage.)

Purity is a Matter of Life and Death

“Far from simply forbidding some acts of immorality, Jesus says God’s law asks for purity and integrity in our hearts and in our thoughts about others,” (Sinclair Ferguson). Jesus’ call for purity seems extreme but it is because He knows that the fight is a matter of spiritual life or death. While He does not literally intend that we should gouge out our eyes, He very much wants us to put to death the earthly deeds and desires of the body (Rom. 8:13; Col. 3:5). We do this in Christ alone, as those raised with Him to new life. In Him we give “no provision for the flesh, to gratify its desires,” (Rom. 13:13-14). We kill sin and give it no foothold in our hearts lest it kills us (from, The Mortification of Sin, by John Owen). Our hearts are hungry with desire. By the Holy Spirit in us we can and must cultivate in them a hunger and thirst for righteousness, holiness, and purity by continually starving them of sinful pleasure and feeding them the heavenly joys of Christ and the things of God’s good and perfect way.

Discussion Questions and Application

  • Take some time to read through and discuss the passages listed above that extol the value and virtues of marriage and sex. What new appreciation do these passages give you for marriage and sex?
  • In his book, The Tech-Wise Family, Andy Crouch cites a study that says pornography accounts for 30% of all internet traffic. That does not include all of the provocative material in advertising, television shows, and movies. Knowing this, what are some practices you already employ to avoid the sin of “looking with lustful intent”? What additional measures, extreme perhaps, can and should you take?
  • Pray that the Spirit would humble you and grow in your heart a desire for sexual purity and a hunger for the glory of Christ.
  • Confess any sexual sin to the Lord. Talk with your spouse, a trusted fellow Christian, or a pastor about accountability in this area