Catechism of the Catholic Church §144 — excerpt
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.
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.