Catechism of the Catholic Church

1137 The book of Revelation of St. John, read in the Church's liturgy, first reveals to us, "A throne stood in heaven, with one seated on the throne": "the Lord God." ¹ It then shows the Lamb, "standing, as though it had been slain": Christ crucified and risen, the one high priest of the true sanctuary, the same one "who offers and is offered, who gives and is given." ² Finally it presents "the river of the water of life . . . flowing from the throne of God and of the Lamb," one of most beautiful symbols of the Holy Spirit. ³

1138 "Recapitulated in Christ," these are the ones who take part in the service of the praise of God and the fulfillment of his plan: the heavenly powers, all creation (the four living beings), the servants of the Old and New Covenants (the twenty-four elders), the new People of God (the one hundred and forty-four thousand), ⁴ especially the martyrs "slain for the word of God," and the all-holy Mother of God (the Woman), the Bride of the Lamb, ⁵ and finally "a great multitude which no one could number, from every nation, from all tribes, and peoples and tongues." ⁶

1139 It is in this eternal liturgy that the Spirit and the Church enable us to participate whenever we celebrate the mystery of salvation in the sacraments.