Catechism of the Catholic Church §199 — excerpt
"I believe in God": this first affirmation of the Apostles' Creed is also the most fundamental. the whole Creed speaks of God, and when it also speaks of man and of the world it does so in relation to God.
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: Roman Catechism I, 2, 2