From Pope St. John Paul II’s Apostolic Exhortation Reconciliatio et Pænitentia (1984):
The church has the mission of proclaiming this reconciliation and as it were of being its sacrament in the world. The church is the sacrament, that is to say, the sign and means of reconciliation in different ways which differ in value but which all come together to obtain what the divine initiative of mercy desires to grant to humanity.
She is a sacrament in the first place by her very existence as a reconciled community which witnesses to and represents in the world the work of Christ.
She is also a sacrament through her service as the custodian and interpreter of sacred Scripture, which is the good news of reconciliation inasmuch as it tells each succeeding generation about God’s loving plan and shows to each generation the paths to universal reconciliation in Christ.
Finally she is a sacrament by reason of the seven sacraments which, each in its own way, “make the church.”52 For since they commemorate and renew Christ’s paschal mystery, all the sacraments are a source of life for the church and in the church’s hands they are means of conversion to God and of reconciliation among people.
52 Cf St. Augustine, De Civitate Dei, XXII 17: Corpus Christianorum, Latin series 48, 835f; St. Thomas Aquinas, Summa Theologiae, III pars, q. 64, art. 2 ad tertium.
— Reconciliatio et Pænitentia 11