*Minor differences ignored. Grouped by changes, with first version listed as example.
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.)
1 - 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.
There is one lawgiver - There is but one who has a right to give law. The reference here is undoubtedly to the Lord Jesus Christ, the great Legislator of the church. This, too, is a most important and vital principle, though one that has been most imperfectly understood and acted on. The tendency everywhere has been to enact other laws than those appointed by Christ - the laws of synods and councils - and to claim that Christians are bound to observe them, and should be punished if they do not. But it is a fundamental principle in Christianity that no laws are binding on the conscience, but those which Christ has ordained; and that all attempts to make other laws pertaining to religion binding on the conscience is a usurpation of his prerogatives. The church is safe while it adheres to this as a settled principle; it is not safe when it submits to any legislation in religious matters as binding the conscience.
Who is able to save and to destroy - Compare Matthew 10:28. The idea here would seem to be, that he is able to save those whom you condemn, and to destroy you who pronounce a judgment on them. Or, in general, it may mean that he is intrusted with all power, and is abundantly able to administer his government; to restrain where it is necessary to restrain; to save where it is proper to save; to punish where it is just to punish. The whole matter pertaining to judgment, therefore, may be safely left in his hands; and, as he is abundantly qualified for it, we should not usurp his prerogatives.
Who art thou that judgest another? - "Who art thou, a weak and frail and erring mortal, thyself accountable to that Judge, that thou shouldest interfere, and pronounce judgment on another, especially when he is doing only what that Judge permits him to do?" See this sentiment explained at length in the notes at Romans 14:4. Compare the Romans 2:1 note, and Matthew 7:1 note. There is nothing more decidedly condemned in the Scriptures than the habit of pronouncing a judgment on the motives and conduct of others. There is nothing in which we are more liable to err, or to indulge in wrong feelings; and there is nothing which God claims more for himself as his peculiar prerogative.
There is one lawgiver - Και κριτης, And judge, is added here by AB, about thirty others, with both the Syriac, Erpen's Arabic, the Coptic, Armenian, Ethiopic, Slavonic, Vulgate, two copies of the Itala, Cyril of Antioch, Euthalius, Theophylact, and Cassiodorus. On this evidence Griesbach has received it into the text.
The man who breaks the law, and teaches others so to do, thus in effect set himself up as a lawgiver and judge. But there is only one such lawgiver and judge - God Almighty, who is able to save all those who obey him, and able to destroy all those who trample under feet his testimonies.
Who art thou that judgest another? - Who art thou who darest to usurp the office and prerogative of the supreme Judge? But what is that law of which St. James speaks? and who is this lawgiver and judge? Most critics think that the law mentioned here is the same as that which he elsewhere calls the royal law and the law of liberty, thereby meaning the Gospel; and that Christ is the person who is called the lawgiver and judge. This, however, is not clear to me. I believe James means the Jewish law; and by the lawgiver and judge, God Almighty, as acknowledged by the Jewish people. I find, or think I find, from the closest examination of this epistle, but few references to Jesus Christ or his Gospel. His Jewish creed, forms, and maxims, this writer keeps constantly in view; and it is proper he should, considering the persons to whom he wrote. Some of them were, doubtless, Christians; some of them certainly no Christians; and some of them half Christians and half Jews. The two latter descriptions are those most frequently addressed.
There is one lawgiver,.... The Alexandrian copy, and others, and the Syriac, Ethiopic, and Vulgate Latin versions, add, "and judge". Who is the one only Lord God, Isaiah 33:22. This is a character that may be applied to God the Father, who gave the law to the people of Israel, both the judicial and ceremonial law, and also the moral law; from his right hand went a fiery law, and to him belongs the giving of it; and also to the Son of God, the Lord Jesus who is King of saints, and lawgiver in his house; who has given out commandments to be observed, and laws of discipline for the right ordering of his house, and kingdom, to be regarded; and particularly the new commandment of love, which is eminently called the law of Christ; and which is most apparently broke, by detraction and speaking evil one of another: now there may be inferior and subordinate lawgivers, as Judah is said to be God's lawgiver, and Moses is said to command the Jews a law; yet there is but one supreme, universal, and perfect lawgiver, who is God; and though there may be many lawgivers in things political, whose legislative power is to be obeyed, both for the Lord's sake, and for conscience sake; yet in things religious, and relating to conscience, God is the only lawgiver, who is to be hearkened unto:
who is able to save, and to destroy; this is true of God the Father, who is able to save, and does save by his Son Jesus Christ, and even persons that have broken the law he has given, and are liable to the curse and condemnation of it; and he is able to save them according to that law, in perfect consistence with it, and with his justice and holiness, since Christ, by whom he saves, was made under it, and has fulfilled it; and that Christ is mighty to save, able to save to the uttermost, is certain from the Scripture, and all experience; and God, the lawgiver, is able to destroy both body and soul in hell, for the transgressions of his law; and even Christ the Lamb is also the lion of the tribe of Judah, who will break his enemies in pieces, as a potter's vessel, and punish the contemners of his Gospel with everlasting destruction, from his presence and glory: in a word, God, the lawgiver, is sovereign, and can destroy, or save, whom he pleases; he is able to save the brother that is spoken against, and to destroy him that speaks against him:
who art thou that judgest another? another man's servant, as in Romans 14:4 or "thy neighbour", as the Syriac and Ethiopic versions read; or "the neighbour", as the Alexandrian copy, and the Vulgate Latin version; that is, any brother, friend, or neighbour, in the manner as before observed in the preceding verse.
There is one lawgiver--The best authorities read in addition, "and judge." Translate, "There is One (alone) who is (at once) Lawgiver and Judge, (namely) He who is able to save and destroy." Implying, God alone is Lawgiver and therefore Judge, since it is He alone who can execute His judgments; our inability in this respect shows our presumption in trying to act as judges, as though we were God.
who art thou, &c.--The order in the Greek is emphatic, "But (inserted in oldest manuscripts) thou, who art thou that judgest another?" How rashly arrogant in judging thy fellows, and wresting from God the office which belongs to Him over thee and THEM alike!
another--The oldest authorities read, "thy neighbor."
There is one lawgiver that is able - To execute the sentence he denounces. But who art thou - A poor, weak, dying worm.
*More commentary available at chapter level.