Our lives ought to make evil things ashamed to show their ugly faces. Christians should be, as it were, the incarnate conscience of a community. The Apostle is not thinking so much of words as of deeds, though words are not to be withheld when needful. The agent of reproof is 'the light,' which here is the designation of character as transformed by Jesus, and the process of reproof or conviction is simply the manifestation of the evil in its true nature, which comes from setting it in the beams of the light. To show sin as it is, is to condemn it; 'for everything that is made manifest is light.' Observe that Paul here speaks of 'light,' not 'the light,'--that is, he is speaking now not of Christian character, which he had likened to light, but of physical light to which he had likened it, and is backing up his figurative statement as to the reproving and manifesting effects of the former, by the plain fact as to the latter, that, when daylight shines on anything, it is revealed, and, as it were, becomes light. He clenches his exhortation by quoting probably an early Christian hymn, which regards Christ as the great illuminator, ready to shine on all drowsy, dark souls as soon as they stir and rouse themselves from drugged and fatal sleep. The second set of exhortations here is connected with the former by a 'therefore,' which refers to the whole preceding precept. Because the Christian is to shake himself free from complicity with works of darkness, and to be their living condemnation, he must take heed to his goings. A climber on a glacier has to look to his feet, or he will slip and fall down a crevasse, perhaps, from which he will never be drawn up. Heedlessness is folly in such a world as this. '"Don't care" comes to the gallows.' The temptation to 'go as you please' is strong in youth, and it is easy to scoff at 'cold-blooded folks who live by rule,' but they are the wise people, after all. A great element in that heedfulness is a quick insight into the special duty and opportunity of the moment, for life is not merely made up of hours, but each has its own particular errand for us, and has some possibility in it which, neglected, may be lost for ever.