John 12:35, “The light is among you for a little longer. Walk whilst you have the light, lest darkness overtake you.”
Thus, the Gospel must be perpetually proclaimed. Not just from the pulpit, but the proclamation of the Gospel continues even after the sermon has ended, and it never stops. For we live in a sinful, corrupt world, which its darkness constantly seeks to overtake us. When we hear the Gospel, we have the light, but we must believe it and perennially proclaim it to ourselves lest we allow the darkness to snuff it out of us. Hence the necessity of meditatio (meditation)—the constant going to, meditation, praying on, and relying on God’s Word. For the less time we spend in the Word, the lesser we trust in God and the easier it is for darkness to overtake us.
The Lutheran Column 