CCC 775 “The Church, in Christ, is like a sacrament – a sign and instrument, that is, of communion with God and of unity among all men.”¹ The Church’s first purpose is to be the sacrament of the inner union of men with God. Because men’s communion with one another is rooted in that union with God, the Church is also the sacrament of the unity of the human race. In her, this unity is already begun, since she gathers men “from every nation, from all tribes and peoples and tongues”;² at the same time, the Church is the “sign and instrument” of the full realization of the unity yet to come.

CCC 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),³ especially the martyrs “slain for the word of God,” and the all-holy Mother of God (the Woman), the Bride of the Lamb,⁴ and finally “a great multitude which no one could number, from every nation, from all tribes, and peoples and tongues.”⁵

CCC 1296 Christ himself declared that he was marked with his Father’s seal.⁶ Christians are also marked with a seal: “It is God who establishes us with you in Christ and has commissioned us; he has put his seal on us and given us his Spirit in our hearts as a guarantee.”⁷ This seal of the Holy Spirit marks our total belonging to Christ, our enrollment in his service for ever, as well as the promise of divine protection in the great eschatological trial.⁸

CCC 2642 The Revelation of “what must soon take place,” the Apocalypse, is borne along by the songs of the heavenly liturgy⁹ but also by the intercession of the “witnesses” (martyrs).¹⁰ The prophets and the saints, all those who were slain on earth for their witness to Jesus, the vast throng of those who, having come through the great tribulation, have gone before us into the Kingdom, all sing the praise and glory of him who sits on the throne, and of the Lamb.¹¹ In communion with them, the Church on earth also sings these songs with faith in the midst of trial. By means of petition and intercession, faith hopes against all hope and gives thanks to the “Father of lights,” from whom “every perfect gift” comes down.¹² Thus faith is pure praise.

1 LG 1.
2 Rev 7:9.
3 Cf. Rev 4-5; 7:1-8; 14:1; Isa 6:2-3.
4 Rev 6:9-11; Rev 21:9; cf. 12.
5 Rev 7:9.
6 Cf. Jn 6:27.
7 2 Cor 1:21-22; cf. Eph 1:13; 4,30.
8 Cf. Rev 7:2-3; 9:4; Ezek 9:4-6.
9 Cf. Rev 4:8-11; 5:9-14; 7:10-12.
10 Rev 6:10.
11 Cf. Rev 18:24; 19:1-8.
12 Jas 1:17.