Matthew 6:22-24 - Dummelow's Commentary on the Bible

Singlemindedness in God's service, and how it is to be attained (Luke 11:34; Luke 16:13). The connexion of thought is—How can we be sure that we are laying up treasure in heaven, and acting simply and purely for the glory of God? Our Lord replies: By paying attention to our consciences, and keeping them in a healthy state. We are too much inclined to believe that our consciences are sure to lead us right, forgetting that the conscience itself may be darkened by sin. Conscience is like the eye. When the eye is in a healthy state the whole body is full of light (Matthew 6:22). Every object is seen in its true colours, true proportions, and accurate position. But if there is a cataract in the eye, or malformation of the lens, or colour-blindness, then the whole body is full of darkness, or distorted light (Matthew 6:23). So it may be with conscience, and therefore we are warned against blindly trusting our consciences, which may, through past sin or from lack of moral education, be seeing things in a false light, or may even be thoroughly corrupt, giving us moral darkness instead of light. We are to put our consciences to school with Jesus Christ, and to be quite sure before we trust them, that they give the same moral judgments and are as sensitive as those of the best Christians. When our consciences are sound, and our souls are full of light, we shall be able to discern whether we are serving God. or mammon. If our consciences are unsound, we may go on serving mammon all our lives without knowing it.