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 (Luke 11:34).
In the previous verse, Jesus says the purpose of light is to illumine the path – so you don’t stumble around in darkness. I would guess we have all had that latter experience. In that sense, the Psalmist says, God’s word is the light to illumine our way to God (Psalm 119:105).
But here, Jesus changes the metaphor. The eye no longer follows the light. The eye is the light, and the body follows it. Jesus’ point is that your life tends in the direction of where you are looking. If you are looking at the wrong things (ie. have an unhealthy eye), you’ll head in the wrong direction – toward darkness.
Eve found the fruit of the forbidden tree “pleasing to the eye.” If I might paraphrase: “she couldn’t keep her eyes off it” and she just kept circling back. The solution of course was easy, but hard. Look at something else. But she didn’t, and before long, she couldn’t. The light that was her eye went bad. It led to discontent and ultimately, sin.
In her essay “My Year of No Shopping” Ann Patchett writes of the year she decided not to buy anything. The decision was born out of two realizations: First, that her shopping had become a (poor) way of handling anxiety and second, she already had far more than she needed. She writes: “The trick of no-shopping wasn’t just to stop buying things. The trick was to stop shopping.” Stop looking – advice that would have saved King David a lot of heartache.
But “stop looking” isn’t only what Jesus has in mind. He calls us to something deeper. Realize what you are looking at, what you are focusing on. Is it necessary? Is it good? Will it make you a better you? Will it contribute to holiness? No? Then turn away and focus elsewhere. In time (unless you keep circling back), you’ll find its hold lessening, the attraction fading and your life will take a turn toward the light and healthiness God always intended.