Luther, AE:53, 41-50: “Therefore, I pray all of you, my dear sirs, let each one surrender his own opinions and get together in a friendly way and come to a common decision about these external matters, so that there will be one uniform practice throughout your district instead of disorder—one thing being done here and another there—lest the common people get confused and discouraged.
For even though from the viewpoint of faith, the external orders are free and can without scruples be changed by anyone at any time, yet from the viewpoint of love, you are not free to use this liberty, but bound to consider the edification of the common people, as St. Paul says, I Corinthians 14 [:40], “All things should be done to edify,” and I Corinthians 6 [:12], “All things are lawful for me, but not all things are helpful,” and I Corinthians 8 [:1], “Knowledge puffs up, but love builds up.” Think also of what he says there about those who have a knowledge of faith and of freedom, but who do not know how to use it; for they use it not for the edification of the people but for their own vainglory.
Now when your people are confused and offended by your lack of uniform order, you cannot plead, “Externals are free. Here in my own place I am going to do as I please.” But you are bound to consider the effect of your attitude on others. By faith be free in your conscience toward God, but by love be bound to serve your neighbor’s edification, as also St. Paul says, Romans 14 [15:2], “Let each of us please his neighbor for his good, to edify him.” For we should not please ourselves, since Christ also pleased not himself, but us all.
But at the same time a preacher must watch and diligently instruct the people lest they take such uniform practices as divinely appointed and absolutely binding laws. He must explain that this is done for their own good so that the unity of Christian people may also find expression in externals which in themselves are irrelevant. Since the ceremonies or rites are not needed for the conscience or for salvation and yet are useful and necessary to govern the people externally, one must not enforce or have them accepted for any other reason except to maintain peace and unity between men. For between God and men it is faith that procures peace and unity.”
Luther (where?): Now even though external rites and orders … add nothing to salvation, it is un-Christian to quarrel over such things and confuse the common people. We should consider the edification of the laity more important than our own ideas and opinions … Let each one surrender his own opinions and get together in a friendly way and come to a common decision about these external matters, so that there will be one uniform practice throughout your district instead of disorder … For even though from the viewpoint of faith, the external orders are free and can without scruples be changed by anyone at anytime, yet from the viewpoint of love you are not free to use this liberty…
Wittenberg Church Order of 1542 (prepared by Jonas, Cruciger, Bugenhagen, Melachthon, Luther, and others; Sehling, I:202): It is the cause of much incorrectness… when the external church ordinances, divine service and ceremonies are not held with reverence, or in orderly fashion, or in like manner. Also certain pastors purpose to act in these matters without uniformity. They shall carefully see to it that the ceremonies which have to do with hymns, clothing of the priests, administration of the sacrament … as well as the festivals, be maintained in an orderly and uniform fashion, at one place as at another, uniform and in accord with such as occur at Wittenberg and Torgau, in accord with the Holy Scriptures…
1569 Church Order of Brauncshweig-Wolfenbuettel (prepared by none other than Martin Chemnitz and Jacob Andreae, the chief authors and architects of the Formula of Concord. Sehling VI.1, 139, 40):Ceremonies [should be instituted] which give the external indication that in the congregation great, high, serious dealings are present, so that the ceremonies lead, stimulate, admonish and move the people to join together their thoughts, lift up their hearts in all humility. That there be in the congregation heartfelt devotion to the word, the Sacrament and prayer … Christian freedom has its place in this matter, as the ancients said, “Disagreement in rites does not take away agreement in faith.” It still brings all sorts of benefit that in ceremonies, so much as it is possible, a uniformity be maintained, and that such uniformity serve to maintain unity in doctrine, and that common, simple, weak consciences be all the less troubled, rather strengthened. It is therefore viewed as good that, as much as possible, a uniformity in ceremonies with neighboring reformed churches be affected and maintained. And for this reason, henceforth all pastors in the churches of our realm, shall emphatically follow this written church order, and not depart from the same without specific, grave cause.
In the exercise of divine worship, certain solemn, public rites should be preserved that aim at good order and decorum and were introduced by the pious consensus of the whole church. Therefore the protection of ecclesiastical rites, which were approved by serious consideration and which give useful instruction concerning many topics in public assemblies, also pertains to the ecclesiastical ministry. Nor should a minister change them, leading to scandal in the church, because of some private desire of his mind. Consequently, the sixth duty of ministers is the preservation of ecclesiastical rites.—Johann Gerhard, On the Ministry II, p. 101.