Expositor's Bible Commentary Commentary Matthew 6:22

"The lamp of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light." — Matthew 6:22 (ASV)

Through the eye the body finds its way. The eye lets in light, and so the whole body is illuminated. But bad eyes let in no light, and the body is in darkness (v.23). The “light within you” is ironic; those with bad eyes, who walk in darkness, think they have light, but this light is in reality darkness. The darkness is all the more terrible for failure to recognize it for what it is (cf. Jn 9:41).

This fairly straightforward description has metaphorical implications. The “eye” can be equivalent to the “heart.” The heart set on God so as to hold to his commands (Psalms 119:10) is equivalent to the eye fastened on God’s law (Psalms 119:18, 148; cf. 119:36–37). Jesus similarly moves from “heart” (v.21) to “eye”.

At the physical level the “whole body” is just that, a body, of which the eye is the part that provides “light.” At the metaphorical level it represents the entire person who is plunged into moral darkness.