Peter deny that he knew Jesus.
In the book of First John, the eighth verse of chapter one talks about sin and that no one is sinless but sinful. Sin is a principle of human nature. We were all born with it at the very beginning. How can we deny it? The verse says, “If we say we have no sin, we deceive ourselves, and the truth is not in us.”
People who say they have fellowship with Christ while living in sin are spiritually blind by their activity. They live in darkness, and in that darkness, they cannot recognize their wrongdoing. The world is a platform for sin. We all have to live in this world that contains evil from the very beginning. Adam and Eve started in the Garden of Eden. Both have instructions by God not to touch one tree, but they can have everything else. All human beings will experience challenges and temptation through the mind where sin is the threat.
Eve, for example, was deceived by the serpent with his words. Then she gave some of the fruit to Adam. Both of them did not realize what happened until they heard the voice of God. Adam was afraid and took Eve to go somewhere and hide. Suddenly, Adam and his wife developed a sense of fear, literally did not tell the truth, and were carnally sensitive. All of these things are what sin represents.
People who claim that they are sinless may be listening to a persuasive spiritual being. We live in this world full of principalities, against various powers, rulers of the darkness of this world, and spiritual wickedness in high places, as mentioned in the book of Ephesians verse twelve of chapter six. The only way for one to have no sin would have to be God or the Son of God to combat those forces described. Otherwise, anyone who claims to be without sin is self-deceived. The things we encounter on earth daily are a potential gateway to sin. For example, wake up in the morning, turn on the radio, find a station with someone talking about some upcoming fitness contest. The thought that could occur is an opportunity for sin with the mind. Turn on the television, flipping through channels, come across a channel with a provocative scene, linger on it long enough could create sin.
The truth is all of us are born in sin and shaped in iniquity, as stated in the fifth verse of Chapter fifty-one of the book of Psalms. While we live, we will do things unknowingly that are sinful. Sometimes, to know the difference between good and evil is by learning or someone letting us know the truth. The world has good and evil. We will need help from God, family, and friends that care to differentiate as we live each day. There is no lone ranger. The truth is all of us have sinned. The problem is living by the truth for it to stay within us.