The Kingdom of God is Within You by Leo Tolstoy Chapter 3 Page 28

consequently holy, is the same church as the Greek Orthodox priesthood profess faith in, is even more arbitrary than the assertions of the Catholics or the Orthodox.

If we admit the idea of a church in the sense Homyakov gives to it — that is, a body of men bound together by love and truth — then all that any man can predicate in regard to this body, if such an one exists, is its love and truth, but there can be no outer signs by which one could reckon oneself or another as a member of this holy body, nor by which one could put anyone outside it; so that no institution having an external existence can correspond to this idea.]

For Lutherans the Church of God coincides with a body of men who recognize the authority of the Bible and Luther's catechism.