I would interpret the first twelve numbered sections of Mediator Dei as an introduction of sorts. We are still deep into an introduction of just what Pope Pius XII was hoping to accomplish with this message to the world’s bishops. In MD 3 he lays out more of the foundation, reminding Catholics of what is “given” in terms of Church teaching and understanding on the liturgy. So we are presented with the Mass, the other sacraments, and “daily prayer,” which I would take to mean the Divine Office. Let’s read:
3. In obedience, therefore, to her Founder’s behest, the Church prolongs the priestly mission of Jesus Christ mainly by means of the sacred liturgy. She does this in the first place at the altar, where constantly the sacrifice of the cross is represented[Cf. Council of Trent Sess. 22, c. 1] and with a single difference in the manner of its offering, renewed.[Cf. Council of Trent Sess. 22, c. 2] She does it next by means of the sacraments, those special channels through which men are made partakers in the supernatural life. She does it, finally, by offering to God, all Good and Great, the daily tribute of her prayer of praise. “What a spectacle for heaven and earth,” observes Our predecessor of happy memory, Pius XI, “is not the Church at prayer! For centuries without interruption, from midnight to midnight, the divine psalmody of the inspired canticles is repeated on earth; there is no hour of the day that is not hallowed by its special liturgy; there is no state of human life that has not its part in the thanksgiving, praise, supplication and reparation of this common prayer of the Mystical Body of Christ which is His Church!”[Encyclical Letter Caritate Christi, May 3, 1932]
Two points on which I’d like to offer commentary:
I have no intention of disputing the representation of Good Friday, the notion of sacrifice is only a part of the entirety of the Paschal Mystery.
No mention here of Scripture, outside of the Psalms and Biblical canticles. Do you think God is worshiped only by explicit praise, and not by the proclamation of the Word? Or was this seen (and may still be to some extent) as a catechetical preface to the celebration of the sacraments?
Anything else on which you would like to comment?