One should, then, speak and act as a person going to be judged according to the law that gives freedom. Speaking and acting cover all of a person’s behaviour. No aspect of life will be exempt from judgment. The standard will be the law of the kingdom, which is the OT as interpreted by Jesus, and Jesus’ own teaching. (In James’s day the NT had not yet been written.) This is not a burdensome standard, but a law that sets us free to serve God. Yet in his teaching Jesus makes it clear that freedom is not licence to do anything we wish. All will stand before him and answer for their obedience or lack of it (Mt. 7:15–23; Lk. 6:43–45).
Two proverbs, Judgment without mercy will be shown to anyone who has not been merciful and Mercy triumphs over judgment, perhaps coming from Jesus himself, close the section and make a bridge to the next. The OT clearly teaches that God is a God of mercy (Dt. 4:31) and that he commands his people to act in the same way (Mi. 6:8; Zc. 7:9). Jesus said, ‘Blessed are the merciful, for they will be shown mercy’ (Mt. 5:7). He also said, ‘In the same way as you judge others, you will be judged, and with the measure you use, it will be measured to you’ (Mt. 7:2). Therefore in not being merciful to the poor they are heaping up strict judgment for themselves. They are not showing mercy in the worldly sphere; they will not receive mercy in the eternal sphere. That mercy triumphs over judgment is also the teaching of Jesus (Mt. 6:14–15; 18:21–35). By showing mercy to others now (which means exhibiting the character of God) they will discover that their own judgment has been reduced. Their cause is not hopeless nor is there any need for them to pile up their own judgment.
Carson, D. A., France, R. T., Motyer, J. A., & Wenham, G. J. (Eds.). (1994). New Bible commentary: 21st century edition (4th ed., p. 1360). Leicester, England; Downers Grove, IL: Inter-Varsity Press.