Luke 11:34-36

Your eye is the lamp of your body. When your eyes are healthy, your whole body also is full of light. But when they are unhealthy, your body also is full of darkness. See to it, then, that the light within you is not darkness. Therefore, if your whole body is full of light, and no part of it dark, it will be just as full of light as when a lamp shines its light on you.”