Catechism of the Catholic Church §155 — excerpt
In faith, the human intellect and will co-operate with divine grace: "Believing is an act of the intellect assenting to the divine truth by command of the will moved by God through grace."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: St. Thomas Aquinas, STh II-II, 2, 9 · Dei Filius 3 · DS 3010