If we say that we have no sin, we are deceiving ourselves and the truth is not in us.
If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.
Matthew 5:46-48
"For if you love those who love you, what reward do you have? Do not even the tax collectors do the same?
"If you greet only your brothers, what more are you doing than others? Do not even the Gentiles do the same?
"Therefore you are to be perfect, as your heavenly Father is perfect.