“But if we walk light, as He is in the light we have fellowship one with another.”
1 John 1:7
John introduces a very profound idea in 1 John 1:3, which has very profound implications—fellowship with God. After the devastation of the Fall of mankind, it has profound significance that we, as sinful people, can have access to this God. Moreover, that we can be restored to Him to the point of fellowshipping with Him is grace-upon-grace.
But this fellowship with Him also has profound implications for those walking in darkness. John shows that God is light. John uses this idea of God being light and Christ being the light many times, but has now transitioned to a new way of applying the idea of God as light. In doing so, he describes an attribute of God, namely His holiness. In the context of 1 John 1, we see that John is making reference to the moral and ethical purity of God (vv. 5-7). “That the concomitant of walking in the light is being purified from every sin suggests that walking in the darkness might best be interpreted here, not simply as walking in ignorance, but as walking in sin.” Consequently, those who are not walking in moral purity cannot know God or fellowship with Him (cf. Heb. 12:14; “without which no one will see the Lord”).
So let’s connect the dot of God’s moral purity to the dot of a fallen brother (or sister) in sin. One of the first places that I take a person who has fallen into sin and they are seeking restoration is 1 John 1. I want them to see the moral purity of God—to grapple with His holiness. Their sin is so problematic because it is not consistent with God’s nature (James 1:17) first-and-foremost. However, the story doesn’t end there: if they want restoration, they need to walk in light. 1 John 1:7 says, “if we walk in the light, as he is in the light, we have fellowship with one another.” Before you move too quickly through this, note that John shows moral purity as restorative for our relationships.
When we walk in light, we are simply reflecting the character of God. And when we do that, we are restoring human relationships around us. One of the implications for those who have fallen into sin (i.e., walked in darkness) is to live their life in utter transparency. Paul said that we are to “expose the deeds of darkness” (Eph. 5:11). What an interesting thought: living in the light suggests a total exposure. How do I know someone is authentically repentant? They are willing to have total exposure in their lives.
Practically, I take counselees to the hidden or dark areas of their life. Where have they been hiding? What do only they know about themselves? What device do they only have access to (i.e., phone, computer, etc.)? What is their dark secret? What do they fear others knowing? Biblically speaking, if they are ever to grow in their integrity they must grow in holiness. And that holiness is cultivated by a sense of coming to the light and walking in it. “But whoever does what is true comes to the light, so that it may be clearly seen that his works have been carried out in God” (John 3:21). They must live a life of ‘light-walking’ if they are to be restored. They must be humble enough to be exposed, and when they are, lasting change is probable.
When a brother has fallen into sin, we point them to a holy God who offers a remedy to their sin (1 John 1:9) and call them to the light. To the adulterer: come to the light. To the wayward child: come to the light. To the crook: come to the light. To the immoral: come to the light. Why? Is it to embarrass them or humiliate them? No, it is to restore them. Come walk in the light, as He is in the light so that you can be right in your relationships—with God and man (v. 7). Be totally exposed and transparent so that you can be totally restored.
 Colin G. Kruse, The Letters of John, The Pillar New Testament Commentary (Grand Rapids, MI; Leicester, England: W.B. Eerdmans Pub.; Apollos, 2000), 65.