The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light (Matthew 6:22).
This verse is part of the discourse on heavenly treasure in contrast to earthly treasure. Verse 24 states, No man can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon. An eye fixed on temporal mammon is an evil eye, and the body is filled with darkness (v.23).
But, a single eye is an eye fixed on the unseen; it is singularly fixed by the indwelling of the Holy Spirit on the object of its devotion: the Lord Jesus Christ. Our text verse notes that this singleness of heart fills the body with light; i.e., the illuminating light of Gods Spirit (Hebrews 10:32). The phrase full of light is one Greek word that is also used to denote the bright cloud (that) overshadowed them (Matthew 17:5) on the Mount of Transfiguration.
For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ. But we have this treasure in earthen vessels, that the excellency of the power may be of God, and not of us. . . . While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal (II Corinthians 4:6,7,18).
The eye of Matthew 6 extends far beyond what our biological camera records. It is the eye of the heart in Ephesians 6:5 and Colossians 3:22. Behold, as the eyes of servants look unto the hand of their masters, and as the eyes of a maiden unto the hand of her mistress; so our eyes wait upon the LORD our God, until that He have mercy upon us (Psalm 123:2). CJH