I just started reading Ron Chernow's biography of Alexander Hamilton (very good so far) and was struck by this description of Hugh Knox, a Presbyterian minister who had a very positive impact on Hamilton's life (pg. 34). Let me quote:
"As a raffish young man, he exhibited a lukewarm piety until a strange incident transformed his life. One Saturday at a local tavern where he was a regular, Knox amused his tipsy companions with a mocking imitation of a sermon delivered by his patron, the Reverend John Rodgers. Afterward, Knox sat down, shaken by his own impiety but also moved by the sermon that still reverberated in his mind. He decided to study divinity...."
Fascinating. A mocking sermon delivered by himself convicted Knox's heart and turned him to God.