I don’t agree with everything Puritan William Ames (1576-1633) said about the church, but I greatly appreciated these statements of his I read today:

Believers do not make a particular church, even though by chance many may meet and live together in the same place, unless they are joined together by a special bond among themselves…

This bond is a covenant, expressed or implicit, by which believers bind themselves individually to perform all those duties toward God and toward one another which relate to the purpose of the church and its edification…

Therefore, no one is rightly admitted into the church except on confession of faith and promise of obedience…

Those who have opportunity to join the church and neglect it most grievously sin against God because of his ordinance, and also against their own souls because of the blessing joined to it. And if they obstinately persist in their carelessness, whatever they otherwise profess, they can scarcely be counted believers truly seeing the kingdom of God.

The Marrow of Theology, pp. 180-181.