Commentating on the Book of Revelation, Michael Barber explains that the heart of the book is a description of the Mass. John, in fact, describes in great detail the heavenly wedding feast of the Lamb, which is exactly what we celebrate every time Mass is said. As Barber says, “in the Mass, we are not merely imitating the heavenly liturgy—we are participating in it.” He shows how each element of the Mass we celebrate today, from the penitential rite to saying the Sanctus, corresponds exactly to this description of the heavenly celebration.