"But if you show partiality, you commit sin, and are convicted by the law as transgressors" (2:9). Even the Old Testament forbade personal favoritism. Leviticus 19:15 taught - "You shall do no injustice in judgment. You shall not be partial to the poor, nor honor the person of the mighty. In righteousness you shall judge your neighbor." Jesus Himself showed no personal favoritism--even His enemies admitted that (cf. Luke 20:21). For a Christian to show partiality is to be a transgressor of the law of Christ; to transgress God's law is to sin (I John 3:4)!
James 2:10,11 reads - "For whoever shall keep the whole law, and yet stumble in one point, he is guilty of all. For He who said, 'Do not commit adultery,' also said, 'Do not murder.' Now if you do not commit adultery, but you do murder, you have become a transgressor of the law." Some of the Christians in the first-century evidently had the notion that since they were obeying God's law in most areas that it was acceptable to be negligent with a few things that they considered to be minor. He told them that they were mistaken.
For them to point out their proper treatment of the rich wouldn't justify them in treating the poor shamefully. If they were trying to be justified in this way, then they'd have to live without making any mistakes! Of course, we know that such isn't possible! But, that's the sort of mindset they had. They wanted to count up all the good things they were doing and then count up all the bad things and say, "See James, we're doing more good than bad! Therefore, we're okay before God." James did not agree! He tried to get them to see that showing partiality is a sin that won't be passed over as if it weren't a violation of God's law. He tells them that if they commit any sin then they are lawbreakers, regardless of which sin it is! He emphasized the inconsistency in trying to claim justification under God's law unless one lives absolutely perfectly under it! The vital lesson being taught here is that man has no authority to tamper with God's laws. Man has no right to obey certain laws while ignoring others that are also applicable.
James continued in 2:12 - "So speak and so do as those who will be judged by the law of liberty." Because of everything that he has just said, he reminds them that ultimately they'll be judged by the law of liberty--not the Old Testament but the New (cf. 1:25; John 12:48). The New Testament doesn't free us from laws; it frees us from sin! That's where the liberty is! So, if you say you love your brother, then love your poor brother also, love your brother with different skin color, and love your uneducated brother. Be consistent and judge righteously! Don't show partiality!
This section closes with 2:13 - "For judgment is without mercy to the one who has shown no mercy. Mercy triumphs over judgment." Here attention is given to God's law of reciprocity. You get what you give, and who can disagree that such a law is just (cf. Matt. 18:21ff)? If we don't show mercy to others, then why should God show mercy to us? Now, don't forget that this passage is addressed to Christians. Those who are outside the body of Christ don't have access to God's mercy until they obey the gospel (regardless of how merciful they are to others; cf. II Thess. 1:7-9). James wants Christians to understand that if we show partiality based on physical circumstances, then our hearts are hard and lacking in mercy. Thus, we shouldn't expect God to judge us favorably! Remember that none of us can stand successfully before God on our own merits. Therefore, we need to be merciful to others for our own sake! When we make our judgments, He wants us to judge righteously, not show favoritism based on external circumstances.
Let us summarize these powerful verses before we close. It is sinful to show partiality. It is wrong to favor the rich over the poor and to treat them unequally. In reality, there is more reason to be partial to the poor than to the rich, because the poor are more likely to be receptive to God's word and the rich are often oppressive and blasphemous. The royal law requires us to treat everyone equally, and to avoid unfair or partial treatment. And, if we expect to obtain God's mercy, we must be merciful in our judgments.