"But the third sort [of Divine Service], which the true type of Evangelical Order should embrace, must not be celebrated so publicly in the square amongst all and sundry. Those, however, who are desirous of being Christians in earnest, and are ready to profess the Gospel with hand and mouth, should register their names and assemble by themselves in some house to pray, to read, to baptize and to receive the sacrament and practice other Christian works. In this Order, those whose conduct was not such as befits Christians could be recognized, reproved, reformed, rejected, or excommunicated, according to the rule of Christ in Matt. xviii. Here, too, a general giving of alms could be imposed on Christians, to be willingly given and divided among the poor, after the example of St. Paul in 2 Cor. ix. Here there would not be need of much fine singing. Here we could have baptism and the sacrament in short and simple fashion: and direct everything towards the Word and prayer and love. Here we should have a good short Catechism about the Creed, the Ten Commandments, and the Lord's Prayer.
In one word, if we only had people who longed to be Christians in earnest, Form and Order would soon shape itself. But I cannot and would not order or arrange such a community or congregation at present. I have not the requisite persons for it, nor do I see many who are urgent for it. But should it come to pass that I must do it, and that such pressure is put upon me as that I find myself unable with a good conscience to leave it undone, then I will gladly do my part to secure it, and will help it on as best I can.
In the meantime, I would abide by the two Orders aforesaid; and publicly among the people aid in the promotion of such Divine Service, besides preaching, as shall exercise the youth and call and incite others to faith, until those Christians who are most thoroughly in earnest shall discover each other and cleave together; to the end that there be no faction-forming, such as might ensue if I were to settle everything out of my own head."
Volume 53, pp. 63-64 of Luther’s Works, American Edition.