John Calvin on John 10:20

20. He hath a devil. They employ the most offensive reproach which they can devise, in slandering Christ, that all may shudder at the thought of hearing him. For wicked men, that they may not be forced to yield to God, in a furious manner, and with closed eyes, break out into proud contempt of him, and excite others to the same rage, so that not a single word of Christ is heard in silence. But the doctrine of Christ has sufficient power in itself to defend it against slanders. And this is what believers mean by their reply,