The Apostle John, writing to Christians says:
1Jn 1:6 If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth:
The implication is that some Christians are walking in darkness but saying that they have fellowship with the Lord, further implying that they are not currently walking in unconfessed sin. One who is born-again, he is not instantly perfected in love and his walk with God is a progressive walk of sanctification.
1Jn 1:7 But 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.
The implication in 1 John 1:7 is that the blood of Jesus Christ is still cleansing us from any sin as we are walking in the light (fellowship with Him), progressively experiencing sanctification and walking in greater righteousness and holiness. "If we walk", is speaking of our continuous walk in this life, not "because we walked", or "when we walked", but IF WE WALK.
1Jn 1:8 If we say that we have no sin, we deceive ourselves, and the truth is not in us.
John is correcting the false notion for those that want to say, they are walking in the light perfectly and have absolutely no sin.
1Jn 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
John's instruction implies that as we continue to walk in the Light we will continue to come to Jesus Christ for forgiveness and cleansing. And, that we can take encouragement from the fact that Jesus Christ can cleanse us in this life from all unrighteousness. But, we have to come to Him, walk in the light (truth) and with humility, confess our sins.
1Jn 1:10 If we say that we have not sinned, we make him a liar, and his word is not in us.
This last verse needs not explanation.
Axehead