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Lust Is Adultery (Matt. 5:27-30)


Matthew 5:21-48 is made up of six examples of the “greater righteous” that Jesus calls his followers to; a righteousness that is not just external but internal. In this second example, Jesus unpacks the deeper implications of the Old Testament prohibition against adultery.


Christians must be ruthless in the fight against lust.


“You shall not murder” seemed like an easy to obey commandment to the Pharisees. So long as you don’t take someone’s life, you can say that you’re blameless in this area. But as Jesus pointed out in verses 21-48, it’s not just the act of murder that is sinful but all that leads up to it: anger. To be sinfully angry with someone then is to break the command to not murder.

Jesus now carries this logic over to the issue of adultery. Like murder, this seemed to the Pharisees like an easy command to obey. Just don’t sleep with someone other than your spouse and you’re in the clear, right? But just as the anger that can lead to the act of murder is sinful, the lust that can lead to the act of adultery is sinful. Those who have indulged in lustful thoughts have broken the commandment “You shall not commit adultery”.

Once again, Jesus is calling on us to treat with far more seriousness an issue that we often don’t think is that big of a deal. We’ll condemn the act of the adultery, sure, but sometimes we won’t think twice about casting that second, longing glance at someone we are not married to. It’s easy to justify these thoughts, and to even treat them as harmless since they’re just thoughts. But as Robert Mounce writes, in God’s eyes, there’s “no well-marked boundary between the desire and the deed”.

Since lusting breaks the command not to commit adultery, and since adultery invites God’s wrath (see Col. 3:5-6), the actions Jesus calls us to in Matthew 5:29-30 make perfect sense. To be clear, Jesus is not encouraging physical mutilation here. After all, if you gouge out your right eye and cut off your right hand, you still have another eye and hand to sin with! What he is saying is that we need to be drastic in the fight against lust.

He’s also saying that the fight against lust might require some great inconveniences to us. But if the outcome of unchecked lust is God’s wrath, then nothing is too precious to sacrifice in the fight against it. Sinclair Ferguson articulates the inconvenience this battle may involve: “There will be pain, tears, blood. There will be ‘withdrawal symptoms’ after the amputation. The consequences seem almost unbearable. But the drastic nature of the remedy is simply the index of the radical danger of the sin. It is not a situation for negotiation. Obedience cannot be negotiated, nor can heaven and hell.”

  • In what ways does Jesus’ teaching here challenge our culture’s thoughts on lust and sexuality? How does it challenge your own?
  • In the fight against lust, is there anything in your life you are afraid to give up for fear that it will seem unbearable?
  • What does it practically look like to walk with community in this area?


Romans 8:13 – “For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live.”

Click here for a PDF of this study guide.