Jerome
Catena Aurea · Matthäusevangelium 6
The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light. 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 that darkness!
This is an illustration drawn from the senses. As the whole body is in darkness, where the eye is not single, so if the soul has lost her original brightness, every sense, or that whole part of the soul to which sensation belongs, will abide in darkness. Wherefore He says, If then the light which is in thee be darkness, how great is that darkness! that is, if the senses which are the soul’s light be darkened by vice, in how great darkness do you suppose the darkness itself will be wrapped?