Angie Smith tipped me off to this quote by John Calvin:
Ultimately the man who comes to obey God will love Him first . . . Let us therefore learn that the love of God is the beginning of religion, for God will not have the forced obedience of men, but wishes their service to be free and spontaneous . . . Lastly we learn that God does not linger over the outward sign of achievement but chiefly searches the inner disposition [motive], that from a good root fruits may grow.