Roman Catechism 21.52

Chapter 21 — Part II: The Sacraments — Holy Orders

Section 52. The External Priesthood — The external priesthood, on the contrary, does not pertain to the faithful at large, but only to certain men who have been ordained and consecrated to God by the lawful imposition of hands and by the solemn ceremonies of holy Church, and who are thereby devoted to a particular sacred ministry.