1 John 1:8 thru 2:2, What is Sin?

⁸ If we say that we have no sin, we deceive ourselves, and the truth is not in us. ⁹ If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. ¹⁰ If we say that we have not sinned, we make him a liar, and his word is not in us.

1 John 1:8-10