Two feelings are compounded all through this passage: an intense sympathy with the purpose of God that the Gospel should be preached to every creature--Paul's very soul melts into that; and an intense scorn for the spirit that sneaks and poaches on another's ground, and is more anxious that some men should be good sectarians than that all men should be good disciples. This evil spirit Paul loathes, just as Christ loathed it; the temper of these verses is that in which the Master cried, "Woe unto you, scribes and Pharisees, hypocrites! for ye compass sea and land to make one proselyte; and when he is become so, ye make him twofold more a son of hell than yourselves." Of course the evil spirit must always be disguised, both from others and from itself: the proselytiser assumes the garb of the evangelist; but the proselytiser turned evangelist is the purest example in the world of Satan disguised as an angel of light. The show is divine, but the reality is diabolical. It does not matter what the special sectarianism is: the proselytising of a hierarchical Church, and the proselytising of the Plymouth Brethren, are alike dishonourable and alike condemned. And the safeguard of the soul against this base spirit is an interest like Paul's in the Christianising of those who do not know Christ at all. Why should Churches compete? why should their agencies overlap? why should they steal from each other's folds? why should they be anxious to seal all believers with their private seal, when the whole world lies in wickedness? That field is large enough for all the efforts of all evangelists, and till it has been sown with the good seed from end to end there can be nothing but reprobation for those who trespass on the province of others, and boast that they have made their own what they certainly did not make Christ's.
At the close, to borrow Bengel's expression, Paul sounds a retreat. He has liberated his mind about his adversaries--always a more or less dangerous process; and after the excitement and self-assertion are over, he composes it again in the presence of God. He checks himself, we feel, with that Old Testament word, "Now he that glorieth, let him glory in the Lord. I _have_ always broken new ground; I _have_ come as far as you, and wish to go farther, evangelising; I never _have_ boasted of another man's labours as if they were mine, or claimed the credit of what he had done; but all this is mine only as God's gift. It is His grace bestowed on me, and not in vain. I would not boast except in Him; for not he who commends himself is approved, but only he whom the Lord commends." No character which is only self-certificated can stand the test: no claim to apostolic dignity and authority can be maintained which the Lord does not attest by granting apostolic success.
NOTE ON VV. 12 AND 13.--In some MSS. (D*, F, G, 109, It., and some Latins) the last two words of ver. 12 and the first two of ver. 13 (οὐ συνιᾶσιν· ἡμεῖς δέ) are omitted. Most editors of the text (Tischdf. vii., Tregelles, Westcott and Hort) seem to think the omission accidental; among exegetes, the fact that it yields an easy and natural, though of course a quite different, sense, has caused some hesitation. Thus Bengel, and recently Schmiedel, reject the words. The latter renders the whole passage: "We do not venture to put ourselves on a level, or to compare ourselves, with certain of those who commend themselves; but in measuring ourselves by ourselves, and comparing ourselves with ourselves, we shall not boast beyond measure, but according to the measure of the rule," etc. This is no doubt intelligible and appropriate enough, and certainly one's first impression is that ἀλλ' αὐτοί in ver. 12 ought to refer to Paul; but as the meaning yielded by the passage with the four words included is equally appropriate, and their insertion immeasurably harder to understand than their omission, it seems preferable to let them stand, in the sense explained above. They are found (with the variation of συνίσασιν for συνιᾶσιν in א*) in א**, B, minusc. Theodoret: in E, K, L, P, the form is συνιοῦσιν. Apparently it is only by an accident that their omission leaves good sense.