11 Speak not evil one of another, brethren. He that speaketh evil of his brother, and judgeth his brother, speaketh evil of the law, and judgeth the law: but if thou judge the law, thou art not a doer of the law, but a judge.
11 Ne detrahatis invicem, fratres; qui detrahit fratri, aut judicat fratrem suum, detrahit legi, et judicat legem; si autem judicas legem, non es factor legis sed judex.
12 There is one lawgiver, who is able to save and to destroy: who art thou that judgest another?
12 Unus est legislator, qui potest servare et perdere: tu, quis es qui judicas alterum?
11 Speak not evil, or, defame not. We see how much labor James takes in correcting the lust for slandering. For hypocrisy is always presumptuous, and we are by nature hypocrites, fondly exalting ourselves by calumniating others. There is also another disease innate in human nature, that every one would have all others to live according to his own will or fancy. This presumption James suitably condemns in this passage, that is, because we dare to impose on our brethren our rule of life. He then takes detraction as including all the calumnies and suspicious works which flow from a malignant and perverted judgment. The evil of slandering takes a wide range; but here he properly refers to that kind of slandering which I have mentioned, that is, when we superciliously determine respecting the deeds and sayings of others, as though our own morosity were the law, when we confidently condemn whatever does not please us.
That such presumption is here reproved is evident from the reason that is immediately added, He that speaketh evil of, or defames his brother, speaketh evil of, or defames the law. He intimates, that so much is taken away from the law as one claims of authority over his brethren. Detraction, then, against the law is opposed to that reverence with which it behooves us to regard it.
Paul handles nearly the same argument in Romans 14, though on a different occasion. For when superstition in the choice of meats possessed some, what they thought unlawful for themselves, they condemned also in others. He then reminded them, that there is but one Lord, according to whose will all must stand or fall, and at whose tribunal we must all appear. Hence he concludes that he who judges his brethren according to his own view of things, assumes to himself what peculiarly belongs to God. But James reproves here those who under the pretense of sanctity condemned their brethren, and therefore set up their own morosity in the place of the divine law. He, however, employs the same reason with Paul, that is, that we act presumptuously when we assume authority over our brethren, while the law of God subordinates us all to itself without exception. Let us then learn that we are not to judge but according to God's law.
Thou art not a doer of the law, but a judge. This sentence ought to be thus explained: "When thou claimest for thyself a power to censure above the law of God thou exemptest thyself from the duty of obeying the law." He then who rashly judges his brother; shakes off the yoke of God, for he submits not to the common rule of life. It is then an argument from what is contrary; because the keeping of the law is wholly different from this arrogance, when men ascribe to their conceit the power and authority of the law. It hence follows, that we then only keep the law, when we wholly depend on its teaching alone and do not otherwise distinguish between good and evil; for all the deeds and words of men ought to be regulated by it.
Were any one to object and say, that still the saints will be the judges of the world, (1 Corinthians 6:2,) the answer is obvious, that this honor does not belong to them according to their own right, but inasmuch as they are the members of Christ; and that they now judge according to the law, so that they are not to be deemed judges because they only obediently assent to God as their own judge and the judge of all. With regard to God he is not to be deemed the doer of the law, because his righteousness is prior to the law; for the law has flown from the eternal and infinite righteousness of God as a river from its fountain.
12 There is one lawgiver  Now he connects the power of saying and destroying with the office of a lawgiver, he intimates that the whole majesty of God is forcibly assumed by those who claim for themselves the right of making a law; and this is what is done by those who impose as a law on others their own nod or will. And let us remember that the subject here is not civil government, in which the edicts and laws of magistrates have place, but the spiritual government of the soul, in which the word of God alone ought to bear rule. There is then one God, who has consciences subjected by right to his own laws, as he alone has in his own hand the power to save and to destroy.
It hence appears what is to be thought of human precepts, which cast the snare of necessity on consciences. Some indeed would have us to shew modesty, when we call the Pope antichrist, who exercises tyranny over the souls of men, making himself a lawgiver equal to God. But we learn from this passage something far more, even that they are the members of Antichrist, who willingly submit to be thus ensnared, and that they thus renounce Christ, when they connect themselves with a man that is not only a mortal, but who also extols himself against him. It is, I say, a prevaricating obedience, rendered to the devil, when we allow any other than God himself to be a lawgiver to rule our souls.
Who art thou. Some think that they are admonished here to become reprovers of their own vices, in order that they might begin to examine themselves, and that by finding out that they were not purer than others, they might cease to be so severe. I think that their own condition is simply suggested to men, so that they may think how much they are below that dignity which they assumed, as Paul also says, "Who art thou who judgest another?" (Romans 14:4.)
 Griesbach adds kai krite^'s, "and judge," a reading favored by many MSS. and the versions; and doubtless it makes the passage more complete, especially as what follows belongs to the judge rather than to the lawgiver, that is, to save or to destroy.