Charles Ellicott Commentary Matthew 6:23

"But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is the darkness!" — Matthew 6:23 (ASV)

If thine eye be evil — If the spiritual faculty, whose proper work is to give light, is itself diseased—if it does not see singly but doubly, and therefore dimly—then the whole life is also shrouded in gloom.

If that is the case with the higher life, what will be the state of the lower? If the light is darkened, what will be the state of the region of life that is naturally dark—the region of appetites and passions, which needs the light's presence to keep them in check?

If the light that is in you is darkness, how great that darkness will be!