If ye fulfill the royal law. The law here I take simply as the rule of life; and to fulfill, or perform it, is to keep it with real integrity of heart, and as they say, roundly, (rotunde;) and he sets such a keeping in opposition to a partial observance of it. It is said, indeed, to be a royal law, as it is the royal way, or road; that is, plain, straight, and level, which, by implication, is set in opposition to sinuous by-paths and windings. Allusion however is made, as I think, to servile obedience which they rendered to the rich, when they might, by serving in sincerity their neighbors, be not only free men, but live as kings. When, in the second place, he says, that those who had respect of persons were convinced, or reproved by the law, the law is taken according to its proper meaning. For since we are bidden by God's command to embrace all mortals, every one who, with a few exceptions, rejects all the rest, breaks the bond of God, and inverts also his order, and is, therefore, rightly called a transgressor of the law.

If ye fulfil the royal law - That is, the law which he immediately mentions requiring us to love our neighbor as ourselves. It is called a "royal law," or kingly law, on account of its excellence or nobleness; not because it is ordained by God as a king, but because it has some such prominence and importance among other laws as a king has among other men; that is, it is majestic, noble, worthy of veneration. It is a law which ought to govern and direct us in all our intercourse with men - as a king rules his subjects.
According to the Scripture, Thou shalt love thy neighbor as thyself - Leviticus 19:18. Compare Matthew 19:19. See it explained by the Saviour, in the parable of the good Samaritan, Luke 10:25-37. In regard to its meaning, see the notes at Matthew 19:19.
Ye do well - That is, "if you fairly comply with the spirit of this law, you do all that is required of you in regulating your intercourse with others. You are to regard all persons as your "neighbors," and are to treat them according to their real worth; you are not to be influenced in judging of them, or in your treatment of them, by their apparel, or their complexion, or the circumstances of their birth, but by the fact that they are fellow-beings." This is another reason why they should not show partiality in their treatment of others, for if, in the true sense, they regarded all others as "neighbors," they would treat no one with neglect or contempt.

The royal law - Νομον βασιλικον. This epithet, of all the New Testament writers, is peculiar to James; but it is frequent among the Greek writers in the sense in which it appears St. James uses it. Βασιλικος, royal, is used to signify any thing that is of general concern, is suitable to all, and necessary for all, as brotherly love is. This commandment; Thou shalt love thy neighbor as thyself, is a royal law, not only because it is ordained of God, and proceeds from his kingly authority over men, but because it is so useful, suitable, and necessary to the present state of man; and as it was given us particularly by Christ himself, John 13:34; John 15:12, who is our King, as well as Prophet and Priest, it should ever put us in mind of his authority over us, and our subjection to him. As the regal state is the most excellent for secular dignity and civil utility that exists among men, hence we give the epithet royal to whatever is excellent, noble, grand, or useful.

(4) If ye fulfil the (f) royal law according to the scripture, Thou shalt love thy neighbour as thyself, ye do well:
(4) The conclusion: charity which God prescribes cannot agree with the respecting of people, seeing that we must walk in the king's highway.
(f) The law is said to be royal and like the king's highway, in that it is simple and without changes, and that the law calls everyone our neighbour without respect, whom we may help by any kind of duty.

If ye fulfil the royal law,.... Which is the law of love to men, without distinction of rich and poor, high and low, bond and free; and is so called, because it is the law of the King of kings; hence the Syriac version renders it, "the law of God", it is the law of Christ, who is King of saints; and because it is a principal law, the chief of laws; as love to God is the sum of the first and great commandment in the law, and may be called the king of laws; so love to the neighbour is the second and next unto it, and may very well bear the name of the queen of laws, and so has royalty in it; and indeed this last is said to be the fulfilling of the law, Romans 13:8 and it is also submitted to, and obeyed by such who are made kings and priests to God; and that in a royal manner, with a princely spirit, willingly, and with all readiness: the same word, in the Hebrew language, signifies "princes", and to be willing. The Jews frequently ascribe royalty to the law, and often speak of , "the crown of the law" (w); and they suppose the Israelites had crowns upon their heads, when the law was given them on Mount Sinai, in which were engraven the name of God, and which they were stripped of when they made the golden calf (x): now this royal law is fulfilled, when it is regarded without respect of persons,
according to the Scripture, in Leviticus 19:18
thou shall love thy neighbour as thyself; and which is to be understood of every nation, without distinction of Jews and Gentiles, and of persons of every state and condition, rich and poor, without any difference: and when this law is so observed, it is commendable:
ye do well: that which is right, and which is a man's duty to do; this, when done from right principles, and to a right end, is a good work, and is doing a good work well.
(w) Pirke Abot, c. 4. sect. 13. & Abot R. Nathan, c. 41. T. Bab. Megilla, fol. 28. 2. Bemidbar Rabba, sect. 4. fol. 183. 2. & sect. 14. fol. 215. 2. & Midrash Kohelet, fol. 73. 4. Targum Jonah in Deut. xxxiv. 5. (x) Vid. Targum. Jonah. & Jerus. in Exod. xxxii. 25. & xxxiii. 4.

The Greek may be translated, "If, however, ye fulfil," &c., that is, as ALFORD, after ESTIUS, explains, "Still I do not say, hate the rich (for their oppressions) and drive them from your assemblies; if you choose to observe the royal law . . . well and good; but respect of persons is a breach of that law." I think the translation is, "If in very deed (or 'indeed on the one hand') ye fulfil the royal law . . . ye do well, but if (on the other hand) ye respect persons, ye practice sin." The Jewish Christians boasted of, and rested in, the "law" (Acts 15:1; Acts 21:18-24; Romans 2:17; Galatians 2:12). To this the "indeed" alludes. "(Ye rest in the law): If indeed (then) ye fulfil it, ye do well; but if," &c.
royal--the law that is king of all laws, being the sum and essence of the ten commandments. The great King, God, is love; His law is the royal law of love, and that law, like Himself, reigns supreme. He "is no respecter of persons"; therefore to respect persons is at variance with Him and His royal law, which is at once a law of love and of liberty (James 2:12). The law is the "whole"; "the (particular) Scripture" (Leviticus 19:18) quoted is a part. To break a part is to break the whole (James 2:10).
ye do well--being "blessed in your deed" ("doing," Margin) as a doer, not a forgetful hearer of the law (James 1:25).

If ye fulfil the royal law - The supreme law of the great King which is love; and that to every man, poor as well as rich, ye do well. Leviticus 19:18.