In his stirring commentary on Psalm 16 (Psalm 16:3) Calvin remarks:
This passage, therefore, teaches us that there is no sacrifice more acceptable to God than when we sincerely and heartily connect ourselves with the society of the righteous, and being knit together by the sacred bond of godliness, cultivate and maintain with them brotherly good-will. In this consists the communion of saints which separates them from the degrading pollutions of the world, that they may be the holy and peculiar people of God.
The community serves, it seems, the dual purpose of knitting believers together in godliness and sanctity and in separating believers from the ‘degrading pollutions’ of the world. Calvin may well be on to something here that modern Christianity might need very much: i.e., the community as refuge. Christianity has never been, and never can be, an individual concern. It is a community of saints, believers gathered together not simply for worship but for fellowship, mutual encouragement, and mutual edification.
In our over-individualized culture what we need, perhaps more than anything, is the security which the communio sanctorum alone offers. Calvin, it is my opinion, understood this and in putting thought to paper has allowed us all to see the value of it as well.