theres alot of context left out of this 1 scripture.
1 John 1:6-10" If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth: 7But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. 8If we say that we have no sin, we deceive ourselves, and the truth is not in us. 9If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. 10If we say that we have not sinned, we make him a liar, and his word is not in us."
its about being forgiven of our sins, and cleansed from all unrighteousness.
1 john 3:5-10 "And ye know that he was manifested to take away our sins; and in him is no sin. 6Whosoever abideth in him sinneth not: whosoever sinneth hath not seen him, neither known him.
Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous. He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.
Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God. In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother."
"If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness..and the blood of Jesus Christ his Son cleanseth us from all sin...... And ye know that he was manifested to take away our sins;....For this purpose the Son of God was manifested, that he might destroy the works of the devil."