The particular reason why Paul calls on them to examine themselves was, that there was occasion to fear that many of them had been deceived. Such had been the irregularities and disorders in the church at Corinth; so ignorant had many of them shown themselves of the nature of the Christian religion, that it was important, in the highest degree, for them to institute a strict and impartial examination to ascertain whether they had not been altogether deceived. This examination, however, is never unimportant or useless for Christians; and an exhortation to do it is always in place. So important are the interests at stake, and so liable are the best to deceive themselves, that all Christians should be often induced to examine the foundation of their hope of eternal salvation.

Whether ye be in the faith. Whether you are true Christians. Whether you have any true faith in the gospel. Faith in Jesus Christ, and in the promises of God through him, is one of the distinguishing characteristics of a true Christian; and to ascertain whether we have any true faith, therefore, is to ascertain whether we are sincere Christians. For some reasons for such an examination, and some remarks on the mode of doing it, See Barnes "1 Co 11:28".

Prove your own selves. The word here used (dokimazete) is stronger than that before used, and rendered "examine," (peirazete.) This word, prove, refers to assaying or trying metals by the powerful action of heat; and the idea here is, that they should make the most thorough trial of their religion, to see whether it would stand the test. See Barnes "1 Co 3:13".

The proof of their piety was to be arrived at by a faithful examination of their own hearts and lives; by a diligent comparison of their views and feelings with the word of God; and especially by making trial of it in life. The best way to prove our piety is to subject it to actual trial in the various duties and responsibilities of life. A man who wishes to prove an axe, to see whether it is good or not, does not sit down and look at it, or read all the treatises which he can find on axe-making, and on the properties of iron and steel, valuable as such information would be; but he shoulders his axe, and goes into the woods, and puts it to the trial there. If it cuts well; if it does not break; if it is not soon made dull, he understands the quality of his axe better than he could in any other way. So if a man wishes to know what his religion is worth, let him try it in the places where religion is of any value. Let him go into the world with it. Let him go and try to do good; to endure affliction in a proper manner; to combat the errors and follies of life; to admonish sinners of the error of their ways; and to urge forward the great work of the conversion of the world, and he will soon see there what his religion is worth -- as easily as a man can test the qualities of an axe. Let him not merely sit down and think, and compare himself with the Bible, and look at his own heart -- valuable as this may be in many respects; but let him treat his religion as he would anything else -- let him subject it to actual experiment. That religion which will enable a man to imitate the example of Paul, or Howard, or the great Master himself, in doing good, is genuine. That religion which will enable a man to endure persecution for the name of Jesus; to bear calamity without murmuring; to submit to a long series of disappointments and distresses for Christ's sake, is genuine. That religion which will prompt a man unceasingly to a life of prayer and self-denial; which will make him ever conscientious, industrious, and honest; which will enable him to warn sinners of the error of their ways, and which will dispose him to seek the friendship of Christians, and the salvation of the world, is pure and genuine. That will answer the purpose. It is like the good axe with which a man can chop all day long, in which there is no flaw, and which does not get dull, and which answers all the purposes of an axe. Any other religion than this is worthless.

Know ye not your own selves. That is, "Do you not know yourselves?" This does not mean, as some may suppose, that they might know of themselves, without the aid of others, what their character was; or that they might themselves ascertain it; but it means that they might know themselves -- that is, their character, principles, conduct. This proves that Christians may know their true character. If they are Christians, they may know it with as undoubted certainty as they may know their character on any other subject. Why should not a man be as able to determine whether he loves God, as whether he loves a child, a parent, or a friend? What greater difficulty need there be in understanding the character on the subject of religion than on any other subject; and why should there be any more reason for doubt on this than on any other point of character? And yet it is remarkable, that while a child has no doubt that he loves a parent, or a husband a wife, or a friend a friend, almost all Christians are in very great doubt about their attachment to the Redeemer, and to the great principles of religion. Such was not the case with the apostles and early Christians. "I know," says Paul, "whom I have believed, and am persuaded that he is able to keep that which I have committed to him," etc., 2 Ti 1:12. "We KNOW," says John, speaking in the name of the body of Christians, "that we have passed from death unto life," 1 Jo 3:14. "We KNOW that we are of the truth," 1 Jo 3:19. "We KNOW that he abideth in us," 1 Jo 3:24. "We KNOW that we dwell in him," 1 Jo 4:13. See also 1 Jo 5:2,19,20.

So Job said, "I KNOW that my Redeemer liveth, and that he shall stand in the latter day upon the earth," etc., Job 29:25. Such is the current language of Scripture. Where, in the Bible, do the sacred speakers and writers express doubts about their attachment to God and the Redeemer? Where is such language to be found as we hear from almost all professing Christians, expressing entire uncertainty about their condition; absolute doubt whether they love God or hate him; whether they are going to heaven or hell; whether they are influenced by good motives or bad; and even making it a matter of merit to be in such doubt, and thinking it wrong not to doubt? What would be thought of a husband that should make it a matter of merit to doubt whether he loved his wife; or of a child that should think it wrong not to doubt whether he loved his father or mother? Such attachments ought to be doubted -- but they do not occur in the common relations of life. On the subject of religion men often act as they do on no other subject; and if it is right for one to be satisfied of the sincerity of his attachments to his best earthly friends, and to speak of such attachment without wavering or misgiving, it cannot be wrong to be satisfied with regard to our attachment to God, and to speak of that attachment, as the apostles did, in language of undoubted confidence.

How that Jesus Christ is in you. To be in Christ, or for Christ to be in us, is a common mode in the Scriptures of expressing the idea that we are Christians. It is language derived from the close union which subsists between the Redeemer and his people. See the phrase explained See Barnes "Ro 8:10".

Except ye be reprobates? See Barnes "Rom 1:28".

The word rendered "reprobates," (adokimoi,) means, properly, not approved, rejected; that which will not stand the trial. It is properly applicable to metals, as denoting that they will not bear the tests to which they are subjected, but are found to be base or adulterated. The sense here is, that they might know that they were Christians, unless their religion was base, false, adulterated; or such as would not bear the test. There is no allusion here to the sense which is sometimes given to the word reprobate, of being cast off or abandoned by God, or doomed by him to eternal ruin in accordance with an eternal purpose. Whatever may be the truth on that subject, nothing is taught in regard to it here. The simple idea is, that they might know that they were Christians, unless their religion was such as would not stand the test, or was worthless.

{a} "yourselves" 1 Co 11:28; 1 Jo 3:20,21

{b} "is in you" Ro 8:10; Ga 4:19 {c} "reprobates" 1 Co 9:27; 2 Ti 3:8