Saint Paisios the Athonite passage in an orthodox blog by the sisters of monasterevmc.org

Humility Makes the Devil Crumble by Saint Paisios

Humility has great power. Humility makes the devil decompose into dust. It is the strongest blow to the devil. Where there is humility, the devil has no place. And if there is no place for the devil, then there is no temptation. Once an ascetic forced a demon to say the Trisagion. “Holy God, Holy Mighty, Holy Immortal!” the demon mumbled and stopped. He did not say, “Have mercy on us”. “Now say, Have mercy on us!” Whoa! Had the demon uttered these words, he would have become an angel. A demon can say whatever you want except “have mercy on us”, because it takes humility to say these words. There is humility in the petition “have mercy on us” and the soul that asks for God’s great mercy receives what it asks for…

With pain and love for contemporary man, vol 1 by Saint Paisios the Athonite