Catechism of the Catholic Church §1211 — excerpt
Following this analogy, the first chapter will expound the three sacraments of Christian initiation; the second, the sacraments of healing; and the third, the sacraments at the service of communion and the mission of the faithful.
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 III, 65, 3