Why did [Jesus] sigh over the man’s tongue [in Mark chapter seven]?
He saw what harm wicked tongues would do in the church, namely, more than all tyrants and persecutors of Christians. When Christians are persecuted, faith increases, love grows more ardent, and God’s Word more powerful, and Satan, the spirit of lies, grows weaker, as do his lies. For the blood of Christians is the seed from which Christians grow. Therefore the persecution of tyrants is not the greatest harm. Rather, the greatest harm is done by that piece of flesh that flaps behind the teeth. It may seem as though great harm is done when a Christians is slain and his head cut off, but a false sermon delivered in the name of Christ is so sharp that in an hour it cuts off a whole land or city of souls. The Turk did great harm to Christendom with sword and armor, but that is a trifle compared with the harm that the papists’ crowd does with their false doctrine. A good Christian might well sigh, indeed, weep tears of blood, at such poisonous, wicked, deceitful tongues – not those which lie or beguile in the marketplace or at home, but those which speak lies or bring to light false doctrine from the pulpit.
– Johann Spangenberg, “The Christian Year of Grace”, translated by Matthew Carver, page 293