Verses 8 to 13 explain that the person who favors the rich at the expense of the poor is showing favoritism. This person is a lawbreaker, having failed to love his or her neighbor. Anyone who breaks part of the law breaks the whole and is to be judged by that law.

If you really fulfill the royal law: the particle translated as really in the Revised Standard Version rendering has two meanings. If it is taken as an adversative, it can be rendered as “however” (so New American Bible, New American Standard Bible). If it is taken as an affirmative, it may be rendered as “indeed” (so New International Version), or “really” (so Goodspeed, Good News Translation). Scholars are divided as to which is the proper meaning here. If “however” is adopted, verse 8 is introducing a contrast with what goes before in verses 2-7, and in effect is a continuation of the argument James is making. It seems better, however, to take the particle as “indeed” or “really,” suggesting that the royal law is really fulfilled only when there is no discrimination. In this case it is related to what follows, introducing a contrast with what is said in verse 9.

In spite of some objections, the phrase royal law is best taken to refer to the command to love your neighbor as yourself (Lev 19.18), the command also quoted by Jesus (Matt 22.39) and Paul (Rom 13.8-9; Gal 5.14). However, the meaning of the adjective royal is interpreted in various ways:
(1) It has been argued that, since verses 10-11 refer to parts of the Ten Commandments, and since in Greek the word law does not have a definite article, the law here refers to the Old Testament law as a whole. And it is described as royal because it was given by the King of heaven. This interpretation is unlikely, in that this same law is referred to as “the law of liberty” in verse 12 and described as “the perfect law” in 1.25, suggesting that it is a reference to the gospel and to the teaching of Jesus in particular. We note that, when James wants to refer to parts of the Ten Commandments (verses 9-11), he uses the word law without a qualifier; but when he wishes to refer to the Christian understanding of law, he invariably uses a qualifier, as above.
(2) The adjective royal is sometimes understood as the law given by or from a king, and in this case the king can either be “God” (so R. P. Martin; compare Die Bibel im heutigen Deutsch “God, the great King”) or “Christ” (so Reicke).
(3) It is also taken to mean “sovereign” (so New English Bible, Revised English Bible) in the sense that the law possesses absolute authority, like that which a king has over his subjects, and that it is unconditionally binding.
(4) It is sometimes interpreted to mean “supreme” (so Goodspeed, New Jerusalem Bible), or “the most important” (Contemporary English Version), suggesting that the command to love ranks as first or most important among others (compare Mark 12.31), just as it is said elsewhere to sum up all other laws (Rom 13.8-9; Gal 5.14).
(5) Picking up the reference to the “kingdom” in verse 5, it seems preferable to understand the phrase as a Kingdom law, that is “the law of the Kingdom,” as Good News Translation has rendered it. This means the law of loving your neighbor is the sovereign rule of the Kingdom of God.

The phrase according to the scripture obviously refers to the Old Testament, and in particular Lev 19.18, the passage quoted.

You shall love your neighbor as yourself is often quoted in the New Testament (eight times) as the summary and the highest principle of the Old Testament Law. In the Old Testament neighbor always means a fellow Jew or countryman, but Jesus expands its usage by including everyone that a person might come into contact with, particularly those in need, even foreigners (Luke 10.25-37) and enemies (Matt 5.44). In the present context it is the poor who are the neighbors in need. In many parts of the world the idea of love is very difficult to translate. Some alternative ways of rendering this term are “care for,” “treat with affection,” or idiomatically, “have a warm [or, sweet] heart [or, liver/stomach] toward.” In this context the ideas of duty or loyalty are foremost, rather than the meaning “like someone very much.” The term neighbor is best translated generally; for example, “other people,” “your own people,” “fellow human beings” and so on.

The clause you do well does not have to be taken in a sarcastic or ironic sense, as the same clause in 2.19 might suggest. It simply says “you are doing the right thing.” In some languages it may be more natural to move this clause to the front as Good News Translation has done (also New Revised Standard Version); thus “You will be doing the right thing if you obey the law of the Kingdom.”

Alternative translation models for this verse may be:
• The most important law in the scriptures that God as our ruler asks us to follow is: “You must love other people as you love yourself.” If you obey this law you will be doing the right thing.
• The most important law … is the one that commands you to love others as much as you love yourselves. If you do this you will be….

Quoted with permission from Loh, I-Jin and Hatton, Howard A. A Handbook on The Letter from James. (UBS Handbook Series). New York: UBS, 1997. For this and other handbooks for translators see here .