66 The mystery of the most Holy Eucharist which Christ, the High Priest instituted, and which He commands to be continually renewed in the Church by His ministers, is the culmination and center, as it were, of the Christian religion. We consider it opportune in speaking about the crowning act of the sacred liturgy, to delay for a little while and call your attention, Venerable Brethren, to this most important subject.
Source: Mediator Dei (Vatican.va)