Dei Filius, On Faith, Canon 5

5. If any one shall say that the assent of Christian faith is not a free act, but inevitably produced by the arguments of human reason; or that the grace of God is necessary for that living faith only which worketh by charity: let him be anathema.

Translation: Henry Edward Manning, Petri Privilegium (1871), reproduced in Philip Schaff, Creeds of Christendom II, via CCEL.