“Who come to you in sheep’s clothing, but inwardly are ravening wolves.”

No one sends them. They come of themselves. And this is the real nature of false prophets, that in order to preach they force themselves upon us. Some do it for a living, which I do not value very highly, for they will not have it quite as easy as they think. But those who force themselves upon us with the boast that they do it for the sake of Christian love, on account of the truth and that the Holy Spirit constrains them to do so; and that they seek nothing but the salvation of souls; of all such be on your guard, for the devil has most certainly sent them, and not God. For those whom God sends are called and constrained to enter upon their work. Nor do they boast much of themselves.  But of whatever they do boast, they prove by their work. Therefore, the Lord would say, beware of those you see are neither sent nor called, but come of themselves at the devil’s call.

— Martin Luther, from a sermon for the Eighth Sunday after Trinity, on Matt 7:15-23