The sight of a rapidly spreading fire is terrifying; James has used the image to stir people to swift and radical action. If we come to the realization that the fire's source is unquenchable, the effect is more sobering; James now uses this fact to call for sustained and disciplined action. For this second warning about the tongue, James changes his imagery and speaks of wild animals. He repeats the verb tame in present and perfect tenses so that we make no mistake about how commonplace it is for human beings to tame wild animals. Yet no human being can tame the tongue.
Why is that so? To explain, in quick succession James adds two phrases referring to the tongue. First, the tongue is a restless evil, untamable because it is inherently unstable and therefore, even when brought under some control, always prone to further evil. This requires that we be continually watchful over our tongues, never thinking we have successfully altered the nature of our speech.
James used the same adjective akatastatos in 1:8 to describe the "unstable" man; he will use the related noun akatastasia in 3:16 to refer to the "disorder" that prevails where humility and wisdom from above are missing. We are left with a picture of this instability as characteristic of unspirituality; it stands in contrast to the peace (eirene) emphasized in 3:17-18.
Second, with a sudden change in imagery, the tongue is full of deadly poison. Again we are compelled to be continually watchful—to keep the lid on the poison, to keep the discipline of our speech in place, because we know the power to destroy with our tongues is present as often as we speak.
From all three images—wild animals, restless evil and deadly poison—the application is the same: discipline. Self-discipline is to be practiced actively and diligently, in recognition of the constant danger. It takes discipline to be "quick to listen, slow to speak and slow to become angry" (1:19). And, looking ahead to the next verse, it will mean controlling what one says to stop verbally abusing people who are made in God's own image.
IVP New Testament Commentaries are made available by the generosity of InterVarsity Press.