Proving what is well pleasing to God:

“"In all goodness," he says: this is opposed to the angry, and the bitter: "and righteousness"; this to the covetous: "and truth"; this to false pleasure: not those former things, he says, which I was mentioning, but their opposites. "In all"; that is, the fruit of the Spirit ought to be evinced in everything. "Proving what is well-pleasing unto the Lord"; so that those things are tokens of a childish and imperfect mind.”

“Above, the Apostle forbade carnal sins, threatening punishment and removing the deception; here he assigns a reason taken from their condition, and he does two things. For first he sets forth their condition; second he draws two conclusions from these, at the place "that you may be children of light," etc. Now he sets down two conditions: first the past one, second the present condition, at "but now light," etc. He says therefore, "you were at one time darkness," that is, blinded by ignorance and error. Above, IV, 18: "having their understanding darkened with darkness." Ps. 81:5: "They have not known, nor understood; they walk in darkness." Likewise, dark through sin. Prov. 4:12: "The way of the wicked is darksome; they know not where they fall." But it should be noted that he does not indefinitely say "darksome," but "darkness"; because just as anyone seems to be what predominates in him — just as the whole city seems to be the king, and what the king does is said to be done by the city — so when sin reigns in a man, then the whole man is called sin and darkness. There follows, "but now light," etc., where he sets down the present condition; as if to say: but now you have the light of faith. Phil. 2:15: "Among whom you shine as lights in the world." Matt. 5:14: "You are the light of the world." But against this it is said of John the Baptist: "he was not the light"; how then are the other faithful called light? I respond: they are not called light by essence, but by participation. Then, when he says "walk then as children of light," etc., he draws two conclusions. For he had said that they had been darkness and that now they are light. And therefore first he concludes that they should conform themselves to what they now are; second, that they should avoid what they formerly were, at "and have no fellowship," etc. The first is divided into two. First he sets down the admonition; second he expounds it, at "for the fruit of the light," etc. He says therefore: because you are now light, you should do the works of light; therefore "walk as children of light." John 12:35: "Walk whilst you have the light," etc. Now he expounds this when he says "for the fruit," etc. Now one walks as a child of light in two ways: first as to the substance, or genus, of the work; second as to the manner, or the intention of the one doing it. First, therefore, he sets down the works which must be done; second, with what intention they ought to be done, at "proving," etc. He says therefore: I have said that you should walk as children of light; now the fruit of light are works that are fruitful and clear. Ecclesiasticus 24:23: "My flowers are the fruit of honor," etc. And this "in all goodness," etc. Where it should be noted that every act of virtue is reduced to three things. For it is necessary that the agent be ordered in himself, toward his neighbor, and toward God. In himself, that he be good in himself, and for this reason he says "in all goodness." Ps. 118:66: "Teach me goodness and discipline and knowledge," etc. Likewise, toward the neighbor through justice; therefore he says "in justice." Ps. 118:121: "I have done judgment and justice," etc. Toward God through knowledge and confession of the truth, and therefore he says "and truth." Zach. 8:19: "For love ye truth and peace." Or otherwise, so that goodness is referred to the heart, justice to the deed, truth to the mouth. Above, IV, 25, and Zach. 8:16: "Speak ye truth every one with his neighbor." Then, when he says "proving," etc., he shows with what intention they ought to work: namely, not abruptly, but "proving," that is, discerning by reason. "Let every one prove his own work," as is said in Gal. 6:4. And this, "what is well-pleasing to God," that is, that you intend to do what pleases God. Rom. 15: "that you may prove what is the good, and the acceptable, and the perfect will of God." Then, when he says "and have no fellowship," etc., he exhorts them not to return to the state which they had left, because, as is said in Gal. 2:18: "For if I build up again the things which I have destroyed, I make myself a prevaricator"; 2 Peter 2:22: "The dog is returned to his vomit, and the sow that was washed to her wallowing in the mire." Now this part is divided into two. First he sets down the admonition; second he assigns the reason, at "for the things that are done by them in secret," etc. The first is again divided into two. First he admonishes them not to do evil; second, that they reprove evils, at "but rather reprove them," etc. He says therefore, "proving what is well-pleasing to God," "and have no fellowship with the unfruitful works of darkness," that is, with carnal works leading to perpetual darkness; which indeed are unfruitful, because they have only a momentary delight, most swiftly passing away. Rom. 6:21: "What fruit therefore had you then in those things, of which you are now ashamed?" Jude 1:12: "Trees of autumn, unfruitful, twice dead, plucked up by the roots, raging waves of the sea, foaming out their own confusion," etc. Likewise, they seek dark places on account of shamefulness, because in them they associate with brute beasts. Job 24:15: "The eye of the adulterer observeth darkness, saying: No eye shall see me; and he covereth his face. In the dark he diggeth through houses," etc. Therefore have no fellowship with these, by imitating, by helping, by consenting. Ecclesiasticus 13:22: "What fellowship hath a holy man with a dog?" But certainly this does not suffice, unless you also reprove them, because, as Augustine says, sometimes God punishes the innocent who associate with them, because some good men do not reprove the evil. Ecclesiasticus 17:12: "And he gave to every one of them commandment concerning his neighbor." And therefore he says "but rather reprove." 2 Tim. 4:2: "Reprove, entreat, rebuke," etc. But do we always sin if we do not reprove? Augustine responds: for what you do not reprove out of the fear of charity — namely, lest he become worse, and being scandalized, afflict the good — you do not sin. But if out of the fear of cupidity — namely, lest he become indignant and you lose his benefits to you — then you sin.”

“For it is a shame even to speak of those things,.... This is a reason, why persons should walk as children of light; why they should prove what is acceptable to God; why they should have no fellowship with the unfruitful works of darkness; why the apostle exhorts to reprove them, and yet does not express what they are; and why they should be reproved rather by deeds than by words: and he tacitly intimates, that if it is a shame to speak of those sins which are done of them in secret, it is much more shameful to commit them; the persons the apostle refers to, are the unconverted Gentiles in general; such who have no inheritance in the kingdom of God, who deceive men with vain words, who are children of disobedience, who are in darkness, and destitute of the Spirit; and it may be that respect may be had to the followers of Simon Magus, the Gnostics, and such like impure professors, by whom the vilest things were done in secret; for sins, works of darkness, will not bear the light; there is a consciousness in men of the evil of sin, unless past feeling, and therefore they do not care that others should know their crimes; and besides, there is an imaginary pleasure in committing sin secretly; but then though these things are secret to men, they are not to God; nor will they always remain secrets, they will be brought to light, and therefore no fellowship should be had with them; and especially when they are of such a scandalous nature, that it is a shame to mention the very names of them.”

“Proving--construed with "walk" (Eph 5:8; Rom 12:1-2). As we prove a coin by the eye and the ear, and by using it, so by accurate and continued study, and above all by practice and experimental trial, we may prove or test "what is acceptable unto the Lord." This is the office of "light," of which believers are "children," to manifest what each thing is, whether sightly or unsightly.”