I have a question to ask. When someone mistakenly sees the nakedness of a woman but flees, though flashing of such image comes to mind, which I bury down inside me, is this a sin? Is it a crack for the devil to enter? Is it neccesary that I confess?
"But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:28).
Accidents can happen. We try to cover our nakedness, but sometimes exposure happens despite our best efforts or because of circumstances. You had the correct reaction to it, you left because of embarrassment over the situation. What you did was not wrong.
What Jesus said was wrong is when a man lusts over a woman. But memories or even temptation is not lust. "But each one is tempted when he is drawn away by his own desires and enticed. Then, when desire has conceived, it gives birth to sin; and sin, when it is full-grown, brings forth death" (James 1:14-15). James says the steps to spiritual death are:
- A desire for something
- A temptation, which is an offer to gain what is desired with the trap that you have to break a law of God to get it.
- Lust, which is an acceptance that breaking God's law is worth getting what you desire.
- Sin, which is the actual breaking of God's law.
- Licentiousness, which is sin full-grown. That is when a person gets to the point that he doesn't care what anyone thinks about his sins, he is going to do it anyway. He thinks he has a license to sin.
- Death. When a person stops caring there is no way to bring him back.
You can't stop desires because they are built into you. You can't stop yourself from getting hungry, thirsty, wanting sex, wanting to be liked, etc. These are all normal, healthy desires. Satan takes those desires and twists them so that it looks like you have to sin in order to get what you want. Thus, you are hungry, realize you have no money, and it becomes tempting to steal a candy bar. Since temptations originate with Satan, you can't stop the temptations either -- you can only reject what Satan offers. "Therefore submit to God. Resist the devil and he will flee from you" (James 4:7). But when you start justifying stealing, such as telling yourself you'll pay the guy back later or that you are owed a candy bar, even though it wasn't offered, then you are committing the sin of lust. This is something you can work against because it is originating with your decisions. If you take the candy bar, then it becomes the sin of stealing. When you've stole things so often that it no longer bothers you and you don't give it a second thought, then you've moved into licentiousness. And there you have died spiritually.
Thoughts of what you saw can't be erased from your mind, but you can choose not to dwell on them. You can't stop Satan from trying to use these memories to tempt you, but you can reject the ideas and not justify them in your head.