In this Apostolic Letter, Pope Francis shares some reflections on the liturgy for all Catholics after his Motu Proprio Traditiones custodes. Focusing on tensions present around the celebration of the liturgy, he calls on Catholics to accept the liturgical reform borne out of Sacrosanctum Concilium, and reaffirms that "The liturgical books promulgated by Saint Paul VI and Saint John Paul II … are the unique expression of the lex orandi [the law of what is prayed] of the Roman Rite."

Calling for a "serious and dynamic liturgical formation" beyond the academic environment, Pope Francis criticises "a heightened personalism of the celebrating style which at times expresses a poorly concealed mania to be the centre of attention", and reminds clergy, faithful and the consecrated alike that "[t]he action of the celebration is the place in which, by means of memorial, the Paschal Mystery is made present so that the baptized, through their participation, can experience it in their own lives. Without this understanding, the celebration easily falls into a preoccupation with the exterior (more or less refined) or into a concern only for rubrics (more or less rigid)."

“With this letter I simply want to invite the whole Church to rediscover, to safeguard, and to live the truth and power of the Christian celebration. I want the beauty of the Christian celebration and its necessary consequences for the life of the Church not to be spoiled by a superficial and foreshortened understanding of its value or, worse yet, by its being exploited in service of some ideological vision, no matter what the hue.” (Desiderio Desideravi 16)