That'll preach!
Something said in response to a quote or phrase when a sermon or a lecture can easily be made from it and it be accurate to scripture or text. Usually said in church when someone agrees with something the preacher says.
Man 1: "True humility is not thinking less of yourself; it is thinking of yourself less."
Man 2: "Amen! That'll preach!"
Man 2: "Amen! That'll preach!"