In the Jesus Manifesto (Matthew 5 – 7), Jesus draws a sharp contrast now between a blind person and a sighted person, and so between the light and darkness in which they respectively live. The eye it the lamp of the body.
I want to be able to see. I don’t want to wander around not being able to see. I want my heart to right with God. Jesus offers me the way. Jesus boldly declares “I am the Light of the world; he who follows Me will not walk in the darkness, but will have the Light of life.”
The eye is the lamp of the body. So, if your eye is healthy, your whole body will be full of light, but if your eye is bad, your whole body will be full of darkness. If then the light in you is darkness, how great is the darkness! ~Jesus | Matthew 6:22-23
This is not literal, of course, as if the eye were a kind of window letting light into the body, but it is a readily intelligible figure of speech. Almost everything the body does depends on our ability to see. We need to see in order to run, jump, drive a car, cross a road, cook, embroider and paint.
The eye ‘illumines’ what the body does through its hands and feet. True, blind people often cope wonderfully, learn to do many things without eyes, and develop their other faculties to compensate for their lack of sight. Yet the principle holds good: a sighted person walks in the light, while a blind person is in darkness. And the great difference between the light and the darkness of the body is due to this small but intricate organ, the eye. If your eye is sound, your whole body will be full of light; but if your eye is not sound, your whole body will be full of darkness. In total blindness the darkness is complete.
All this is factual description. But it is also metaphorical. Not infrequently in Scripture the ‘eye’ is equivalent to the ‘heart’. That is, to ‘set the heart’ and to ‘fix the eye’ on something are synonyms.
One example may be enough, from Psalm 119. In verse 10 the psalmist writes: ‘With my whole heart I seek thee; let me not wander from your commandments,’ and in verse 19, ‘I have fixed my eyes on all your commandments.’ Similarly, here in the Jesus Manifesto, Jesus passes from the importance of having our heart in the right place to the importance of having our eye sound and healthy.