If we say that we have fellowship with him while we are walking in darkness, we lie and do not do what is true; but if we walk in the light as he himself is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin. (1 John 1: 7)
This needs to be read, I think, with verses 8-10 as well:
If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. If we say we have not sinned, we make him a liar, and his word is not in us.
As well as the reason the author of 1 John is saying all this:
My little children, I am writing these things to you so that you may not sin. But if anyone does sin, we have an advocate with the Father, Jesus Christ the righteous.
There is much to say on this, but I feel I lack the time. How is it that we can, at the same time, acknowledge our continuing sinfulness and yet be confident in our salvation? I think the answer has something to do with the time God has allotted for our sanctification, which begins here, but continues on after death. With an infinite span of time ahead, God will make something of us yet! And some day, we will be able to say there is no more fault in us; we will be as we should be, as we were meant to be.