Light and darkness are frequently put for holiness and wickedness, Luke 16:8 Romans 13:12 Ephesians 5:8 1 Thessalonians 5:5. The sum then is: That if any pretend to friendship with God, or to have received holy and gracious influences from him, and do yet lead wicked lives, they are liars, even guilty of a practical lie, doing what makes their profession false and insincere.
Related Commentaries of 1 John 1:6
1 John 1:6
6 If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth: