There is agreement among commentators that the basic point of the instruction in 5:12 is to ensure the integrity of one's speech without having to rely on oaths. "Let your `yes' be true and your `no' be true" (Dibelius 1976:249). Additional issues surrounding the verse have to do with (1) the relationship of 5:12 with Matthew 5:33-37, (2) the relationship of 5:12 with the rest of James's text and (3) the specific ways James would intend this verse to be applied. Some observations of the text to investigate the first two issues will clarify the meaning of 5:12 so that we can arrive at some reliable answers to the third and most important question of application.
This instruction is one of James's clearest references to the Sermon on the Mount (Mt 5:33-37), giving further confirmation of his deliberate remembrance of Jesus' teaching. James and Matthew recall Jesus' teaching with the same terms and order. In that teaching Jesus confronted the Pharisaic practice of using various formulas to create different levels of oaths, some of which were considered less binding than others. (Cf. Mt 23:16-22.) The Pharisees could thereby bind themselves to their promises in various degrees and so excuse themselves from keeping commitments they had made with lesser oaths. They could use their oaths to sound exceedingly pious and to justify themselves as deeply religious, while being in fact hypocritical. (See Stott's discussion of Mt 5:33-37, 1978:99-102.) Jesus commanded his followers therefore not to swear but to invest their simple words of yes or no with complete integrity. James follows that passage; we might conclude that he is simply prescribing honesty in speech.
But in two ways James departs from what Matthew records. First, James lends a priority to this particular point of behavior by his introductory above all. Second, James concludes with a warning of judgment (literally, "that you may not fall under judgment," translated "or you will be condemned" in NIV). This is not to imply that James and Matthew disagree about what Jesus said. James is making a reference to what Jesus said and then adding the particular emphases he wants to make. The introductory words above all indicate that James has in mind a meaning larger than honesty in everyday speech. After all he has said about large issues of purity and patience and perseverance, why would he settle upon oaths as the sin to avoid above all? His concluding mention of judgment draws upon the context in 5:1-6 and 5:9, but it also adds further weightiness to this matter of oaths. Why would James make it such a priority?
To answer this we must address the second issue, concerning the context for 5:12 in the epistle. Dibelius blinds himself to this avenue of investigation by insisting that 5:12 "has no relationship with what precedes or follows" (1976:248). It is certainly proper to investigate the context for a possible connection. If the surrounding text provides a reasonable context to explain a verse, and if there is no textual evidence for regarding the verse as a later addition, then there is no basis for rejecting the observed context as the intended context for the verse. We can investigate the matter by asking simple inductive questions. First, does the context tell us anything about why these Christians would be swearing with oaths? Then, does this contextual reason for swearing connect to any fundamental issue in James's letter?
First we consider the preceding context. Throughout the letter and especially in the preceding passage, James has been concerned to encourage his readers' patience and perseverance in the midst of trials. It is clear that he anticipates in their suffering the temptation to compromise their moral standards and so become polluted by the world. He has just been telling them about the need for patience in the face of suffering. In the immediately subsequent context, we will find James prescribing prayer as the proper recourse for Christians in trouble. This context does in fact provide a readily understandable and very possible reason for these Christians to be swearing with oaths. They would be tempted to strike bargains with God, swearing to do one thing or another if only God would deliver them from their persecutors. Religious people have tried this kind of bargaining all through the centuries. Animists who live in fear of their gods are driven to make such promises. The unconverted young Martin Luther made his famous promise to become a monk when a bolt of lightning terrified him in 1505. James has been saying, "Be patient in your suffering. Remember the Lord is coming. Remember the example of the prophets. Remember the perseverance of Job. Remember the Lord's full compassion and mercy." Now he says, "Above all, don't fall into swearing, as if you could manipulate God by your oaths. Instead, speak honestly and directly, and rely on God in prayer."
Does this contextual reason for swearing connect to any issue so fundamental in the letter that James would make this a matter of encompassing importance? It connects to the underlying issue of the entire letter: the meaning and practice of faith. From the very beginning, James has said that his readers' faith is being tested in the trials (1:3). In the midst of trials, Christians are to ask God in faith (1:6). It is because they hold faith in Christ that they are not to show favoritism (2:1). It is faith that constitutes true riches (2:5). James has gone to great lengths to emphasize that genuine faith will manifest itself in deeds (2:14-26). His whole letter is a plea for his readers to be not merely religious people, but people of faith.
Now it is the lack of faith that must appall James in the act of swearing. It is unbelief that would move his readers to try to save themselves by a manipulative use of oaths. It is through lack of faith that we disbelieve God's "compassion and mercy" and so want to strike a bargain. Striking a bargain with God cuts at the very heart of the gospel; it is an attempt to rely on the worth of one's own offering instead of relying on God's grace in the offering of Christ on the cross. Bargaining is a reliance on works; James is insisting that we rely on grace. He is again teaching the opposite of what some have portrayed as an anti-Pauline works-righteousness. James says above all and you will be condemned because he is addressing not just a simple matter of dishonesty but a fundamental lack of faith and denial of grace. Above all makes sense if it introduces not just 5:12 but this entire final section of the letter, in which faith is the real focal point.
Now we can see the proper application of 5:12. We are getting sidetracked if we focus on whether Christians should take oaths in courts of law. We are being too superficial if we see this verse merely as an injunction against "frivolous and indiscriminate oaths and the thoughtless mention of the divine name" because such speech would violate God's law and hinder one's witness to unbelievers (Tasker 1983:125). Those are important matters, but James is here (as usual) cutting to an essential difference between genuine and false religion. He is saying: Do not allow suffering to pressure you into unbelief. Do not try to impress each other or to manipulate God as if your works were what counted instead of God's grace. If you are trusting in God's grace, you have no need to impress God or people, and you can be at peace with saying honest words. Integrity should characterize Christians, and integrity will flow from wholehearted reliance on grace. Unbelief manifests itself in bargaining, manipulating and trying to impress. The opposite manifestation, flowing from faith, will be prayer.