As a conclusion and a climax of his argument, James defines sin, not in terms of doing what is forbidden by God, but in failing to do what we know to be the right thing to do. It is the sin of omission.

Whoever knows what is right to do and fails to do it, for him it is sin: there is a change from second person plural to third person singular at this point. The shift to a more impersonal tone indicates that James may be quoting a well-known proverbial saying.

The Revised Standard Version rendering, unfortunately, fails to bring out the connection between verses 16 and 17 that is there in Greek. The connective word is rendered variously; for example, “So” (Goodspeed, New American Bible), “then” (New International Version, New Revised Standard Version), “So then” (Barclay, Good News Translation), “Well then” (Phillips), “What it comes to is” (Revised English Bible). While we recognize that in Greek there is an obvious attempt to make a connection, we have to admit that it is by no means easy to figure out the precise relationship with the previous section. A number of attempts have been made, without much success, to relate the saying to the section(s) that come before this. One observation, however, may be made. It is quite possible that James, having told his readers what is right to do—that is, not to leave God out of their future but to take him into all of their plans—now wants to warn them as well as to encourage them that if they fail to do it they commit sin. Looking at it from another angle, it may be that James wants his readers to know that the “sin of omission” (failing to do what is right) is no less serious than the “sin of commission” (being presumptuous in leaving God out of their plans). However, if we are not convinced of a real connection here, an alternative is to take this verse as a summary of the important teachings in the previous sections. In this case we may want to make verse 17 a separate paragraph, as Good News Translation has done (so also Luther 1984, Phillips, Die Bibel im heutigen Deutsch).

The clause what is right to do is literally “to do good” (King James Version). The word “good” is an opposite of the word “evil” in verse 16. If the word is rendered as “evil” in verse 16, it will be good to have the word “good” here; thus, for example, “the good he ought to do” (New International Version). On the other hand, if we render the word “evil” in verse 16 as “wrong,” it will be appropriate to have the word “right” here; thus “the right thing to do” (Revised English Bible, New Revised Standard Version). For him it is sin means it is a sin on his part, and the clause may be rendered as “he commits sin” (similarly New Revised Standard Version) or “we are guilty of sin” (Good News Translation).

Alternative translation models for this verse are:
• So, if we don’t do what we know is right, we have sinned.
• So, if you don’t do what you know is right, you have sinned (Contemporary English Version).

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 .