Boasting Before the Devil
It would be very much in order were we to employ such arrogance when addressing the devil and say, I have God’s Word and I know that with it I have accomplished much good–some I have instructed, others I have admonished, here I have helped some with charitable gifts; I know these to be good works in spite of the devil’s slander. I say, we may boast before the devil, because we have received nothing from him. But toward God, from whom we have everything, we may not boast; rather we must humble ourselves.
Luther, House Postil, Sermon for the Eleventh Sunday after Trinity (first sermon, part 11)