Roman Catechism 15.56

Chapter 15 — Part II: The Sacraments — Introduction on the Sacraments in General

Section 56. The Ministers of the Sacraments — But although God is the author and dispenser of the Sacraments, He nevertheless willed that they should be administered in His Church by men, not by Angels. To constitute a Sacrament, as the unbroken tradition of the Fathers testifies, matter and form are not more necessary than is the ministry of men.