Your eye is the lamp of your body

What else does he mean by “the eye” than simply the mind, which will never become simple unless it contemplates the simple light? The simple light is Christ. He who has his light shining in his mind is said to have the mind of Christ. When your light is this simple, then the whole immaterial body of your soul will be full of light. If the mind is evil, that is, darkened and extinguished, then this body of yours will be full of darkness….We say, “See to it, brothers, that while we seem to be in God and think that we have communion with him we should not be found excluded and separated from him, since we do not now see his light.” If that light had kindled our lamps, that is, our souls, it would shine brightly in us. Our God and Lord Jesus Christ said, “If your whole body is full of life, having no dark part, it will be wholly bright, as when a lamp with its rays gives you light." St. Symeon the New Theologian