I know there are many reasons why we should not sin. It causes damage to the relationship with God (Isaiah 59:1,2). It hurts other people. The 2nd great commandment is to love your neighbor and the “golden rule” is to “do unto others as you would have them do unto you. Sin is a trespass against man and God.
But another important reason to flee from sin and immorality is because of the strong temptation to lie against the truth. James says, “But if you have bitter jealousy and selfish ambition in your heart, do not be arrogant and so lie against the truth” (Jas. 3:14). To lie against the Truth leads to a lot of hurt for ourselves and others. When sin is in our lives so that we wish to keep it a secret, we must lie against the truth all the time. Every time the ugly Truth encounters us, the one practicing sin must go to war against it. Elders will go to war with Elders and Preachers will go to war against Elders and Christians will go to war against Teachers because they are hiding something. Satan has a hold of these so that they pridefully conceal their true issue and so they attack those who might expose them, they lie against the Truth. If you are on the receiving end of this attack, it is a difficult time. On the receiving end of the attack, you have God and His Truth on your side, but sometimes it will feel like you are fighting a phantom. The person seems to be religious but dreadfully mistaken about doctrine. But the venom is coming from something inside, lusts. These “liars” against the Truth may be protecting themselves or others, but they have made a decision to go to war and God’s people will bear the brunt of the troubles.
Paul says it will be punished. “For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness,” (Rom. 1:18). Inside these people know the truth about God and they know they truth about themselves, but they have lusts to cover up and so they arrogantly put on a bold face of self-righteousness and go to war against the Truth. They act as if they are on a righteous mission to correct others when what they are really doing is covering up, suppressing the Truth. As long as their lusts are in their hearts, they fight heaven and earth to keep from being exposed.