Ad Catholici Sacerdotii §40

⁴⁰ It is impossible to treat of the piety of a Catholic priest without being drawn on to speak, too, of another most precious treasure of the Catholic priesthood, that is, of chastity; for from piety springs the meaning and the beauty of chastity. Clerics of the Latin Church in higher Orders are bound by a grave obligation of chastity; so grave is the obligation in them of its perfect and total observance that a transgression involves the added guilt of sacrilege.