1 John 1:5-6 ESV

“This is the message we have heard from him and proclaim to you, that God is light, and in him is no darkness at all.  If we say we have fellowship with him while we walk in darkness, we lie and do not practice the truth.”

Thousands, possibly millions of people claim that they believe in God but their actions show they actually do not have a relationship with God. That’s what John is exhorting here. If someone walks in darkness (sin), and they say that they have fellowship with God, they are lying to themselves and others. Actions have to follow the image we portray and testimony we speak.