Read Chapter 27(THE CATHOLIC CHRISTIAN CHURCH) of the Belgic Confession

We believe and profess one catholic or universal church,1which is a holy congregation and assembly2of the true Christian believers, who expect their entire salvation in Jesus Christ,3are washed by His blood, and are sanctified and sealed by the Holy Spirit.4This church has existed from the beginning of the world and will be to the end, for Christ is an eternal King who cannot be without subjects.5This holy church is preserved by God against the fury of the whole world,6although for a while it may look very small and as extinct in the eyes of man.7Thus during the perilous reign of Ahab, the Lord kept for Himself seven thousand persons who had not bowed their knees to Baal.

Moreover, this holy church is not confined or limited to one particular place or to certain persons, but is spread and dispersed throughout the entire world.98However, it is joined and united with heart and will, in one and the same Spirit, by the power of faith.9