sin is sin

R.C. Sproul in The Holiness of God:

We tend to think that sin is sin and that no sin is greater than any other. We think of Jesus' teaching in the Sermon on the Mount that to lust after a woman is to be guilty of adultery. We are aware that the Bible teaches if we sin against one point of the law, we sin against the whole law. These two biblical teachings can easily confuse us about the degrees of sin.

When Jesus said that to lust is to violate the law against adultery, He did not say or imply that lust is as bad as the full act of adultery. His point was that the full measure of the law prohibited more than the actual act of adultery. The law has a broader application. The Pharisees thought that because they never committed the actual act of adultery, they were free of sin against the law. They assumed that if they actually refrained from killing people, they were keeping the law against killing. They failed to see that unjust anger and hatred were also included in the wider meaning of the law against killing.

HT:AH