on Matthew 6 :22
The light of the body is the eye - That is, the eye is to the body what the sun is to the universe in the day time, or a lamp or candle to a house at night.
If - thine eye be single - Απλους, simple, uncompounded; i.e. so perfect in its structure as to see objects distinctly and clearly, and not confusedly, or in different places to what they are, as is often the case in certain disorders of the eye; one object appearing two or more - or else in a different situation, and of a different color to what it really is. This state of the eye is termed, Matthew 6:23, πονηρος evil, i.e. diseased or defective. An evil eye was a phrase in use, among the ancient Jews, to denote an envious, covetous man or disposition; a man who repined at his neighbor's prosperity, loved his own money, and would do nothing in the way of charity for God's sake. Our blessed Lord, however, extends and sublimes this meaning, and uses the sound eye as a metaphor to point out that simplicity of intention, and purity of affection with which men should pursue the supreme good. We cannot draw more than one straight line between two indivisible points. We aim at happiness: it is found only in one thing, the indivisible and eternal God. It the line of simple intention be drawn straight to him, and the soul walk by it, with purity of affection, the whole man shall be light in the Lord; the rays of that excellent glory shall irradiate the mind, and through the whole spirit shall the Divine nature be transfused. But if a person who enjoyed this heavenly treasure permit his simplicity of intention to deviate from heavenly to earthly good; and his purity of affection to be contaminated by worldly ambition, secular profits, and animal gratifications; then, the light which was in him becomes darkness, i.e. his spiritual discernment departs, and his union with God is destroyed: all is only a palpable obscure; and, like a man who has totally lost his sight, he walks without direction, certainty, or comfort. This state is most forcibly intimated in our Lord's exclamation, How great a darkness! Who can adequately describe the misery and wretchedness of that soul which has lost its union with the fountain of all good, and, in losing this, has lost the possibility of happiness till the simple eye be once more given, and the straight line once more drawn.
on Matthew 6 :22
The light of the body ... - The sentiment stated in the preceding verses - the duty of fixing the affections on heavenly things - Jesus proceeds to illustrate by a reference to the "eye." When the eye is directed steadily toward an object, and is in health, or is single, everything is clear and plain. If it vibrates, flies to different objects, is fixed on no one singly, or is diseased, nothing is seen clearly. Everything is dim and confused. The man, therefore, is unsteady. The eye regulates the motion of the body. To have an object distinctly in view is necessary in order to correct and regulate action. Rope-dancers, that they may steady themselves, fix the eye on some object on the wall, and look steadily at that. If they should look down on the rope or the people, they might become dizzy and fall. A man crossing a stream on a log, if he will look across at some object steadily, will be in little danger. If he looks down on the dashing and rolling waters, he will become dizzy, and fall. So Jesus says, in order that the conduct may be right, it is important to fix the affections on heaven. Having the affections there - having the eye of faith single, steady, unwavering - all the conduct will be correspondent.
Single - Steady, directed to one object. Not confused, as persons' eyes are when they see double.
Thy body shall be full of light - Your conduct will be regular and steady. All that is needful to direct the body is that the eye be fixed right. No other light is required. So all that is needful to direct the soul and the conduct is, that the eye of faith be fixed on heaven; that the affections be there.
If, therefore, the light that is in thee ... - The word "light," here, signifies "the mind," or principles of the soul. If this is dark, how great is that darkness! The meaning of this passage may be thus expressed: The light of the body, the guide and director, is the eye. All know how calamitous it is when that light is irregular or extinguished, as when the eye is diseased or lost. So the light that is in us is the soul. If that soul is debased by attending exclusively to earthly objects - if it is diseased, and not fixed on heaven how much darker and more dreadful will it be than any darkness of the eye! Avarice darkens the mind, obscures the view, and brings in a dreadful and gloomy night over all the faculties.
on Matthew 6 :22
6:22 The eye is the lamp of the body - And what the eye is to the body, the intention is to the soul. We may observe with what exact propriety our Lord places purity of intention between worldly desires and worldly cares, either of which directly tend to destroy. If thine eye be single - Singly fixed on God and heaven, thy whole soul will be full of holiness and happiness. If thine eye be evil - Not single, aiming at any thing else.