My husband and I read in the forum every day... and enjoy studying with you all. This was a really good post and definitely deeper than it would appear in light reading of the Word. We used our Sword Searcher Software and found this in the Pulpit Commentary. Thought it might be good to add in here.
The light of the body; the lamp (Revised Version); o lucnoV.1 The thought of the power which treasure has of attracting the heart forms the transition to the need of a pure and steady "eye" heavenwards. The bodily eye is taken as the symbol of the outlooking power of the soul, not the soul—the inner man—itself, but its outlooking power. As the body is illuminated by the eye, i.e. as by the eye the bodily constitution learns its environment, and naturally, almost automatically, tends to accommodate itself to it, so is it with the gaze of the soul. If this be upon the things of this world, the soul perceives, and tends to accommodate itself to the things of this world; if upon things in heaven, it perceives, and tends to accommodate itself to, the things in heaven. The Authorized Version "light" is, therefore, imperfect, for the gaze of the soul is not "light" (jwV), but a "lamp" (lucnoV). As the bodily eye is not itself light, but only an instrument for receiving and imparting light, so in the mere gaze of the soul there is no inherent light, but it is the means of receiving and imparting light to the soul. If therefore thine eye be single. The word "single" (aplouV) presents some difficulty.
(1) If it meant "undivided," it would doubtless continue the illustration of the lamp, with an undivided as contrasted with a divided wick, but it has no such meaning.
(2) It states the opposite, not to divisions, but to folds (vide Trench, 'Syn.,' §56); it is "single" as opposed to "plicate," and therefore can hardly contain any direct reference to the lamp. Its meaning rather appears to be purely metaphorical, and the word seems to be applied 'directly to the functions of the eye in relation to the body. If the eye be "single" and (to use another but related metaphor) straightforward in its working, then the body receives through it the light that it ought to receive. So is it with the gaze of the soul in its effect on the inner man.
(3) Perhaps, however, aplounh is here used in the sense of non-compound (cf. Plato, 'Rep.,' 547. E); in this case free from any foreign substance to bar the light from passing through it. Thy whole body shall be full of light (jwtino). Well-lighted in itself, and bright in appearance to others.2 The word chosen seems to indicate, not merely that the body is, through the eye, lighted, but also that it itself becomes in measure, like the eye, full of light for others. All one's powers become illumined with the Divine light, and the illumination shines through. But if thine eye be evil, etc. Evil (ponhroV); ver. 13, note. Vitiated, worthless. As an eye that does not fulfil its natural function, so is that gaze of the soul which is directed only earthward. To limit tiffs, with Lightfoot ('Hor. Hebr.'), to covetousness, is far too partial an interpretation. Such an earthward and selfish gaze of the soul may often issue in selfishness as regards money,3 but the full meaning of the phrase includes very much more. Thy whole body shall be full of darkness. What the heart craves to see it sees; but in this case, not light makes its entrance, but darkness, which, as in the case of the light, permeates the frame. If therefore the light that is in thee be darkness; rather, is darkness; the change here to the indicative (ei... estin) indicating that the last preceding clause is assumed as fact. The light that is in thee. Our Lord does not say, "the light that comes through the eye," for he means more than this, viz. that the very information, so to speak, brought first by the outlook of the soul, comes into us and remains in us. He assumes that this, which ought to be light, is darkness. How great is that darkness! i.e. the darkness (Revised Version)just spoken of, which comes through the eye. So, probably, Lu 11:35. If the gaze which should bring light brings only darkness, how terrible in its nature and effects must that darkness be! It is, however, possible to understand our Lord to refer in this verse to the natural darkness of the soul before it looks out of itself. In this case the thought is—you need a fixed gaze heavenwards; if your gaze is not heavenwards, it brings darkness instead of light; how black, then, must be the natural darkness!
Lord, help us to keep our gaze HEAVENWARD!!!
God bless your day
Connie