“How great a forest is set ablaze by a small fire! And the tongue is a fire. The tongue is an unrighteous world among our members, staining the whole body, setting on fire the cycle of nature, and set on fire by hell. For every kind of beast and bird, of reptile and sea creature, can be tamed and has been tamed by humankind, but no human being can tame the tongue — a restless evil, full of deadly poison.”
— James 3:5-8

Given the immediate context of the passage, I think James is talking about teachers and building on his comment of why we should not easily presume to become one. It is too easy to use that position to destroy people, to encourage followers not just to benefit from our ideas and insights but to adopt our attitudes, our biases, and even our hatreds. Think of how polarizing a pastor can make his pulpit, or how pundits can whip us into a frenzy against those whom they disagree with.

But more generally the point is that our tongue is the source of the greatest evil in our lives, a theme the psalmist memorably focused on, time and again.

It’s one thing to criticize the president’s health care policy, or to provide moral objections to supply side economics. But when we start calling the president a dictator, or compare Bush to the Nazis, and ascribe all sorts of evil motives to them, we’ve forgotten our place, and allowed our loose tongues to start fires.

I do remember a Pentecostal preacher making the argument that glossalalia is evidence that even the tongue can be fully subject to God, since when we pray in tongues we do not know what we are saying. Support for that would be in Acts 2, when the first Christians were speaking in tongues they themselves did not know, and thousands of people around them understood exactly what was being said, because it was in their own native languages.