5 This is the message which we have heard from Him and declare to you, that God is light and in Him is no darkness at all. 6 If we say that we have fellowship with Him, and walk in darkness, we lie and do not practice the truth. 7 But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin. (1 John 1:5–7, NKJV)
What does it mean to walk in the light? This verse gives us a definitive definition: “Practice the truth” (v. 6) is equivalent to “walk in the light” (v. 7). Fellowship with God comes to those who “walk in the light” – those who practice His truth (His word, John 17:17). We lie if we say we have fellowship with God, yet “do not practice the truth” (v. 6). The God of light is found in the light of truth, not in the darkness of error. According to verse 7, two things happen when one walks in the light: 1) He has fellowship with God, and 2) The blood of Christ cleanses him from all sin. This verse does not say the Christian does not sin (see v. 10). It says the blessing of cleansing from sin by Christ’s blood occurs when we walk in the light. Because this person practices truth (walks in the light), he does not deny his sin when it happens, he confesses it, with the assurance of God’s forgiveness (1 John 1:8-9; Acts 8:22-24).