By his Revelation, "the invisible God, from the fullness of his love, addresses men as his friends, and moves among them, in order to invite and receive them into his own company." The adequate response to this invitation is faith.
By faith, man completely submits his intellect and his will to God. With his whole being man gives his assent to God the revealer. Sacred Scripture calls this human response to God, the author of revelation, "the obedience of faith".
To obey (from the Latin ob-audire, to "hear or listen to") in faith is to submit freely to the word that has been heard, because its truth is guaranteed by God, who is Truth itself. Abraham is the model of such obedience offered us by Sacred Scripture. The Virgin Mary is its most perfect embodiment.
Catechism of the Catholic Church, Part 1, Section1, Chapter 3, #'s 142-144