Barnes New Testament Notes

Verse 8. If ye fulfil the royal law. That is, the law which he immediately mentions requiring us to love our neighbour 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 neighbour as thyself. Le 19:18. Compare Mt 19:19. See it explained by the Saviour, in the parable of the good Samaritan, Lu 10:25-37. In regard to its meaning, see Barnes on "Mt 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 neighbours, 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 "neighbours," they would treat no one with neglect or contempt.

{a} "Thou shalt love thy neighbor as thyself" Le 19:18