1 John 1:7
But if we walk in the light, as he is in the light, we have fellowship one with another…
When they were laying the Atlantic cable the engineers found the communication interrupted, and when they had taken it up sufficiently they found the difficulty was occasioned by a small piece of wire, only about twice the length of a pin, which, by some means, had been driven through the covering of the cable, and carried off the electric fluid. So a very small thing will put us out of fellowship with God, and interrupt our communion with heaven, and the only secret of a constant communion is a constant cleansing from all sin.
Parallel VersesKJV: But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin.