Luke 11:33-36 (ESV)
"No one after lighting a lamp puts it in a cellar or under a basket, but on a stand, so that those who enter may see the light.  Your eye is the lamp of your body. When your eye is healthy, your whole body is full of light, but when it is bad, your body is full of darkness.  Therefore be careful lest the light in you be darkness.  If then your whole body is full of light, having no part dark, it will be wholly bright, as when a lamp with its rays gives you light."
What Jesus says here is mysterious. A person reads it and wonders how a body can be full of light, or full of darkness, how the light in you can be darkness? A person reads this and might wonder what it is that Jesus is speaking of at all. You come across passages that don’t readily open their meaning to you when you read scripture. It’s good not to get frustrated and read on. Later what you do understand will help give you the key to what you don’t understand. Scripture interprets scripture is the Lutheran understanding. The clear sheds light on the dark. These are not times to make up something nonchalantly and then squeeze the other verses to fit your preconceived understandings.
In any case, to shed some light on the dark, I cheated a bit. I am loving Bo Giertz’s commentaries. They get me to thinking. The light in you being darkness. I think Jesus is describing the self-righteous who have latched on to a false gospel.
The gospel is the light that Jesus is speaking of here. It lights up a person’s whole body. It is a wonderful thing. The forgiveness of sins in the death and resurrection of Christ, unequivocally applied to you in baptism. Jesus has done it all. He is your wisdom, he is your righteousness, your sanctification, your redemption. See to it that your whole body is full of this light, no part being dark. But this is how it happens. Darkness sets in because people will believe that Jesus is their righteousness, but not their sanctification. This is the problem in the protestant world, especially since Wesley. Darkness sets in, because sanctification has been divorced from baptism, divorced from the gospel, it is now something you have to do, something you have to grow in. It pulls your eyes away from Jesus who is your sanctification. Makes you think one of two things. Either that you have done it, or you are not sanctified, and if any of these two thoughts are yours, darkness is setting in. This is a particular problem in many Lutheran circles, especially when they talk of Sanctification in a wide and narrow sense. The old saying goes, that in the wide sense Sanctification is about the gospel. But in the narrow sense it is up to you and good works. We are Lutheran in the wide sense, reformed in the narrow sense, a house divided that cannot stand.
The light is the gospel. When it lights up your body, it shines. When darkness sets in it doesn’t. I look back on life, and marvel at times. I have known people who worried about their sanctification. These are the kind of people who will pride themselves on not cussing, or drinking or smoking, never minding that the Bible says nothing concerning two, and the other one it merely cautions moderation. But this is there sanctification. I’ve seen people associate their sanctification with diets, and all sorts of other things. They think they are being good Christians when they are offended by someone’s language. No. This is where darkness sets in, you just come off as a pious prick. You have made Christianity about you. You do not shine. You are darkness. But when you let the gospel shine through all of you. When you realize your only hope is the death and resurrection of Christ, then the gospel starts shining. When you aren’t offended by another’s language, then perhaps you can even have a conversation with them. Keep it up they might even let you tell them about Christ over a beer.