Believers have two forces within them. Before knowing Christ, there was only darkness. Now light has entered, and these forces clash. Paul explains this in Romans 7: 'I find a law: when I want to do good, evil is with me. I delight in God's law inside, but another law in my body fights my mind, trapping me in sin.' This happens because 'the Lord divided the light from the darkness.' Darkness alone is calm, but when God brings light, conflict begins and will last until we're fully light in the Lord.

If a believer is divided inside, there will be division outside too. When God gives us light, we separate from the dark world. We leave superficial, worldly religion behind for the true gospel of Christ. We turn away from worldly society and shallow amusements to stay in the company of believers, for 'We know we've passed from death to life, because we love the brethren.' Light gathers with light, and darkness with darkness. We shouldn't try to unite what God has divided. As Christ left the camp to bear reproach, we must also leave the ungodly and be a distinct people. He was holy and separate from sinners. Just like Him, we're to be different from the world, standing apart from sin, and marked by our resemblance to Jesus.