In verse 7 of 1 John 1, we are encouraged to “walk in the light.” Light reveals truth. The light reveals the truth concerning God, ourselves, and Jesus. Now that we know the truth, we are to live in the truth. However, though we are in Christ, we still have a sin nature we must contend with. In John’s day there were those leaving the church and claiming that they were not guilty of sin. “The expression ‘to have sin’ (echō hamartian) is found only here in 1 John, but it occurs four times in the Fourth Gospel (John 9:41; 15:22, 24; 19:11), and in each case it means to be guilty of sins. Allowing this usage to guide us, we would have to say that what the secessionists were claiming was, not that they were by nature free from the sin principle, but that they were not guilty of committing sins, by which they probably meant they had not sinned since they came to know God and experienced the anointing.” However, such a claim is irresponsible and irrational. In this passage we see several principles relating to the reality of sin and the prospect of forgiveness.
The Principle of Sin. Verse 8 says, “If we say that we have no sin, we deceive ourselves, and the truth is not in us.” Even though we have been born-again and indwelled by the Holy Spirit, as long as we are in theses earthly bodies, we are still sinners. We cannot deny the fact of our sin nature. To do so is deceptive. John takes it a step further to say that if we make such a claim to have no sin, then the truth is not in us. Jesus is the truth. Therefore, for someone to claim to have no sin, they do not have Jesus. They are not truly born-again. A true believer will never make such a claim. Why is this? Because the closer we are to the Lord, the more the light reveals the truth concerning ourselves that we are depraved sinners. The closer we are to the Lord, the greater our sin comes to light. As we grow in Him, we become more aware of our sinfulness and of His holiness and the more appreciative of His grace we become. In verse 10, John says, “If we say that we have not sinned, we make Him a liar, and His Word is not in us.” The Word of God very clearly reveals our sinfulness. The more we are in the Word, the more we are aware of this fact. Therefore, John once again states that someone who says they have no sin, is not truly saved. A true Christian understands the fact of their sin nature and is in a constant battle to bring that nature under submission to the cross of Jesus Christ. Warren Wiersbe writes, “The fact that Christians sin bothers some people—especially new Christians. They forget that their receiving the new nature does not eliminate the old nature they were born with. The old nature (which has its origin in our physical birth) fights against the new nature which we receive when we are born again (Gal. 5:16–26). No amount of self-discipline, no set of man-made rules and regulations, can control this old nature. Only the Holy Spirit of God can enable us to “put to death” the old nature (Rom. 8:12–13) and produce the Spirit’s fruit (Gal. 5:22–23) in us through the new nature. Sinning saints are not mentioned in the Bible to discourage us, but to warn us.” Our fellowship with the Lord and with each other can never be strengthened unless we grasp this principle of sin. Our fellowship can never be strengthened if there are those amongst us with a holier than thou attitude that thinks they can do no wrong. It is only when we are humble, and we realize just how weak we are that we can be made strong. We must face the reality of our sin nature and live with the understanding that none of us are perfect, and we all must struggle with this sin nature until the redemption of our physical bodies.
The Principle of Confession. In the first part of verse 9, we read, “If we confess our sins….” “In countering his opponents’ claim to be sinless John urges his readers to confess their specific sinful deeds, that is, the evil they are actually doing.” We will never have complete victory over our sin nature in this life. Such complete victory will only come when we are glorified and made to be just like Jesus. However, we can have victory over specific acts of sin. We can overcome sinful habits. We can be changed. We can live holy in this life. Living such a life free of acts of sin is possible when we first face the reality of our sin and confess. Confession is not simply admitting that we have sinned. Confession is seeing our sin the way God sees it. It is to agree with God concerning our sin. “To confess, used in connection with sins, means “to avow one’s sins,” “to say openly that one has sinned,” “to accuse oneself of one’s own evil deeds.” Various idiomatic expressions are used, for example, ‘to pull out the heart’ (that the sins in it may be clearly seen), ‘to count up one’s sins’; or, bringing out the purifying function of confession, ‘to cause one’s sin to say good-by,’ ‘to whiten the stomach.’ Sometimes one must make explicit the implied direct discourse, for example, ‘to say, “It is true, I have done evil.” And it may be desirable to add a reference to God, “if we confess our sins to God” (TEV), ‘if we say openly before (or in the presence of) God that we have sinned.” Confession of sin to God is agreeing with God concerning our sin. It is seeing our sin the way God sees it. It is to see the ugliness of our sin in light of the cross. The cross is a very ugly picture. It was on the cross that the sins of the whole world were placed upon Jesus. All the blood, the agony, the pain; it is all a picture of our sin. What God sees concerning our sin is His Son beaten to where He does not look human and nailed to a cross where all of His blood is drained from His body. “Confession is not praying a lovely prayer, or making pious excuses, or trying to impress God and other Christians. True confession is naming sin—calling it by name what God calls it: envy, hatred, lust, deceit, or whatever it may be. Confession simply means being honest with ourselves and with God, and if others are involved, being honest with them too. It is more than admitting sin. It means judging sin and facing it squarely.” Confessing the specific acts of sin that we commit should not be taken lightly. To truly confess is to agree with God. It is to see our sin the way God sees it. It is to see our sin place upon Jesus. “In modern times some have occasionally denied that a Christian needs to confess his sins and ask forgiveness. It is claimed that a believer already has forgiveness in Christ (Eph. 1:7). But this point of view confuses the perfect position which a Christian has in God’s Son (by which he is even “seated … with Him in the heavenly realms” [Eph. 2:6]) with his needs as a failing individual on earth. What is considered in 1 John 1:9 may be described as “familial” forgiveness. It is perfectly understandable how a son may need to ask his father to forgive him for his faults while at the same time his position within the family is not in jeopardy.”  As Christians, we need to be the habit of confessing our sins to the Lord. Such confession strengthens our fellowship with Him.
The Principle of Forgiveness. Verse 9 says, “If we confess our sins, He is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.” This is one of the most beautiful verses in all the Word of God. Notice a few things we learn here about forgiveness. (1) He is Faithful. Every time we confess our sins, He forgives us. When we come before the throne of God and confess our sins, we can rest assured that we are forgiven. He is always faithful to us, and He always forgives. Oh, that we could be faithful to Him as He is faithful to us! (2) He is Just. God always does the right thing. He is always fair. He forgives the sins of anyone and everyone who come to Him by faith no matter who they are and no matter how great their sin. He has the authority to forgive sin and He faithfully forgives every time. (3) He Cleanses us from all Unrighteousness. When we confess our sins, He forgives us of the sins we confess and the sins we fail to confess. He forgives us completely. He wipes our slate clean. Praise the Lord!
The Principle of the Advocate. In 1 John 2:1, we read, “My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous.” John is writing to believers in Christ, and he lays out his purpose for writing to them. The goal is that every Christian would live a life of holiness. That is why we have the Bible. It is given to us to reveal our sin and our need for a Savior and to instruct us in how we can live a life that is pleasing to God. Conforming to the image of Christ is the ultimate goal. Our entire life is to be lived with the goal in mind to become more and more like Jesus. However, we still have a sin nature. Even in our striving for holiness, we still sin. The good news is that we have an advocate that understands our situation and stands ready to forgive us. An advocate is one who stands in the gap for someone else. It is one who defends. Jesus stands before God the Father as our advocate. He stands in our place and defends us.
The Principle of Propitiation. Verse 2 says, “And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.” Propitiation means to appease the wrath of God or to satisfy God’s righteous demands. On the cross of calvary, Jesus satisfied God’s righteous demands on sin. Our sins have been paid for. Both the sins of believers and unbelievers have been paid for. The only difference is that the believer has accepted that payment as their own by faith in Jesus. “How completely sufficient is the blood of Jesus Christ! Enough for the whole world, it surely is enough for you and me.”
Because of what Jesus did for us on the cross, and because of His continual grace and forgiveness, we are to move on in our walk with Him and allow the Holy Spirit to work in us to make us just like Jesus. John encourages us to walk in the light. However, to do so, we must trust in our advocate, the Lord Jesus Christ. To have fellowship with Christ and for that fellowship to grow, we must move toward holiness. We must be constantly aware of our sin, confess our sins, and trust in the One who has paid the price for our sin. “Let us then go on boldly, with full confidence in Him, and walk in the light. We are moving toward holiness. But on the journey, we do not need to hide our sins. We need to acknowledge them, and receive not only forgiveness but the purifying power of our God.”
 Walvoord, J. F., & Zuck, R. B., Dallas Theological Seminary. (1985). The Bible Knowledge Commentary: An Exposition of the Scriptures (Vol. 2, p. 886). Wheaton, IL: Victor Books.