"The sacred mystery of the Church's unity" (UR 2)
What are these bonds of unity? Above all, charity "binds everything together in perfect harmony." But the unity of the pilgrim Church is also assured by visible bonds of communion:
- profession of one faith received from the Apostles;
-common celebration of divine worship, especially of the sacraments;
- apostolic succession through the sacrament of Holy Orders, maintaining the fraternal concord of God's family.
Source: Catechism of the Catholic Church (Vatican.va)