Matthew 6:23

Ver. 22,23. You had need look to your hearts, your understanding, judgment, and affections; for look what proportion there is betwixt your bodily eye and the rest of the bodily members, with regard to their guidance and conduct, the same proportion there is betwixt your heart and whole conversation, with reference to the guidance of it with relation to God. The eye is the window by which the soul looks out to guide the body; if that be not impaired by the defluxion of humours, &c., but be single, it directs all the motions of the body right; but if that be defective, or any way impaired, the whole body is at a loss how to move safely, and with advantage to it. So if your hearts be set right, if you have a right and sound judgment, a true and sanctified affection, they will influence and guide all your actions, your whole conversation will be regular and holy: but if that inward eye be evil, through covetousness, too much adherence to the earth, or through envy, (both which are called evil eyes in Scripture), or through the prevalence of any other lusts or passions, your darkness will be exceeding great, you will not be able to set one step right; for out of the abundance of the heart the mouth speaketh, and according to the dictates and affections of the heart the hand and the whole man acts.