The extended community that is known as the church consists of all the people who have the church within them. The church takes hold in us when we are regenerated, and we are all regenerated when we abstain from things that are evil and sinful and run away from them as we would run if we saw hordes of hellish spirits pursuing us with flaming torches, intending to attack us and throw us onto a bonfire.
As we go through the early stages of our lives, there are many things that prepare us for the church and introduce us into it; but acts of repentance are the things that actually produce the church within us. Acts of repentance include any and all actions that result in our not willing, and consequently not doing, evil things that are sins against God.
Before repentance, we stand outside regeneration. In that condition, if any thought of eternal salvation somehow makes its way into us, we at first turn toward it but soon turn away. That thought does not penetrate us any farther than the outer areas where we have ideas; it then goes out into our spoken words and perhaps into a few gestures that go along with those words. When the thought of eternal salvation penetrates our will, however, then it is truly inside us. The will is the real self, because it is where our love dwells; our thoughts are outside us, unless they come from our will, in which case our will and our thought act as one, and together make us who we are. From these points it follows that in order for repentance to be genuine and effective within us, it has to be done both by our will and by thinking that comes from our will. It cannot be done by thought alone. Therefore it has to be a matter of actions, and not of words alone.
The Word makes it obvious that repentance is the beginning of the church. John the Baptist was sent out in advance to prepare people for the church that the Lord was about to establish. At the same time as he was baptizing people he was also preaching repentance; his baptism was therefore called a baptism of repentance. Baptism means a spiritual washing, that is, being cleansed from sins. John baptized in the Jordan river because the Jordan means introduction into the church, since it was the first border of the land of Canaan, where the church was. The Lord himself also preached that people should repent so that their sins would be forgiven. He taught, in effect, that repentance is the beginning of the church; that if we repent, the sins within us will be removed; and that if our sins are removed, they are also forgiven. Furthermore, when the Lord sent out his twelve apostles and also the seventy, he commanded them to preach repentance. From all this it is clear that repentance is the beginning of the church.
from True Christianity, Section 510