James was dealing with sin that was destroying the NT churches of the scattered and dispersed believing Jews.
Here were professed believers meeting TOGETHER in the churches that were full of discord, contention, and fighting! You expect behavior like this in the world, (remember this, we'll come back to it), but what a terrible thing when this happens among God's people, in church gatherings!
In James went right to the root of the problem, these wars, these fights that are happening "AMONG YOU" are coming from "WITHIN" YOUR own hearts,