177 Since the opinions expressed by some about frequent confession are completely foreign to the spirit of Christ and His Immaculate Spouse and are also most dangerous to the spiritual life, let Us call to mind what with sorrow We wrote about this point in the encyclical on the Mystical Body. We urgently insist once more that what We expounded in very serious words be proposed by you for the serious consideration and dutiful obedience of your flock, especially to students for the priesthood and young clergy.
Source: Mediator Dei (Vatican.va)