1 John 1:6 If we claim to have fellowship with him yet walk in the darkness, we lie and do not live by the truth.
2:11 But whoever hates his brother is in the darkness and walks around in the darkness; he does not know where he is going, because the darkness has blinded him.
John 3:19 This is the verdict: Light has come into the world, but men loved darkness instead of light because their deeds were evil.
John 8:12 When Jesus spoke again to the people, he said, “I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life.”
John 12:35 Then Jesus told them, “You are going to have the light just a little while longer. Walk while you have the light, before darkness overtakes you. The man who walks in the dark does not know where he is going.
2 Corinthians 6:14 Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness?
Ephesians 5:8-10 For you were once darkness, but now you are light in the Lord. Live as children of light (for the fruit of the light consists in all goodness, righteousness and truth) and find out what pleases the Lord.
1 John 2:4 The man who says, “I know him,” but does not do what he commands is a liar, and the truth is not in him.
1 John 4:20 If anyone says, “I love God,” yet hates his brother, he is a liar. For anyone who does not love his brother, whom he has seen, cannot love God, whom he has not seen.
John 8:55 Though you do not know him, I know him. If I said I did not, I would be a liar like you, but I do know him and keep his word.
All of the major translations are very similar here. Notice that it reads “live by the truth”, not “speak the truth.” Many translations read “practice the truth” or “do not the truth”. The distinction is important. Someone who claims to have a relationship with God but walks in the darkness is not just telling a lie, but is living a lie. Someone who lives a lie is, by definition, a liar.
While this is a poignant truth, it is also really very simple. As was made quite clear in verse 5, there is no darkness at all in God, nor can there be. Therefore anyone who is living in darkness cannot, by definition, have any kind of relationship with Him, regardless of any claims to the contrary.
This speaks very directly to the (unfortunately large) group of people who claim to be Christians, but whose lifestyle is indistinguishable from the rest of the world. They may indicate verbally that they “believe in God,” or “are a Christian,” or they may allow it to be implied by their church attendance. These same people who dress nicely for church on Sunday morning may have stumbled home in a drunken stupor the night before. Neither verbal claim nor church attendance are true qualifiers of someone who has a relationship with God. Those who try to pass themselves off in that way are not just lying, they are liars.
JFB indicates that fellowship with God is “the essence of Christian life.”