Traditions regarding kneeling

In the matter of kneeling also prayer is subject to diversity of observance, through the act of some few who abstain from kneeling on the Sabbath; and since this dissension is particularly on its trial before the churches, the Lord will give His grace that the dissentients may either yield, or else indulge their opinion without offense to others. We, however (just as we have received), only on the day of the Lord’s Resurrection ought to guard not only against kneeling, but every posture and office of solicitude; deferring even our businesses lest we give any place to the devil.

At fasts, moreover, and Stations, no prayer should be made without kneeling, and the remaining customary marks of humility; for (then) we are not only praying, but deprecating, and making satisfaction to God our Lord. Touching times of prayer nothing at all has been prescribed, except clearly “to pray at every time and every place.”

Tertullian
On Prayer
Chapter XXII

The 2nd century Church prayed toward the east and worshipped on Sunday

Others, with greater regard to good manners, it must be confessed, suppose that the sun is the god of the Christians, because it is a well-known fact that we pray towards the east, or because we make Sunday a day of festivity.

Tertullian
Ad Nationes, Book I
Chapter XIII

External orders should be chosen carefully

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.

…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

Martin Luther
The Freedom of a Christian

For Luther, worship style is a balance

Those who devise and ordain universal customs and orders get so wrapped up in them that they make them into dictatorial laws opposed to the freedom of faith. But those who ordain and establish nothing succeed only in creating as many factions as there are heads, to the detriment of that Christian harmony and unity of which St. Paul and St. Peter so frequently write.

Martin Luther
A Christian Exhortation to the Livonians Concerning Public Worship and Concord

All that matters to Luther for the Mass was the Words of Institution and faith

But in all these matters we will want to beware lest we make binding what should be free, or make sinners of those who may do some things differently or omit others. All that matters is that the Words of Institution should be kept intact and that everything should be done by faith. For these rites are supposed to be for Christians…who observe them voluntarily and from the heart, but are free to change them how and when ever they may wish. Therefore, it is not in these matters that anyone should either seek or establish as law some indispensable form by which he might ensnare or harass consciences. Nor do we find any evidence for such an established rite, either in the early fathers or in the primitive church, but only in the Roman church. But even if they had decreed anything in this matter as a law, we would not have to observe it, because these things neither can nor should be bound by laws.

Martin Luther
An Order of Mass and Communion for the Church at Wittenberg

Luther states that Christ does not really care about worship style

I have no intention of cramping anyone’s freedom or of introducing a law that might again lead to superstition. Christ will not care very much about these matters, nor are they worth arguing about.

Martin Luther
An Order of Mass and Communion for the Church at Wittenberg

Luther didn’t change worship style more only because the people couldn’t handle it

Until now I have only used books and sermons to wean the hearts of people from their godless regard for ceremonial… For I have been hesitant and fearful, partly because of the weak in faith, who cannot suddenly exchange an old and accustomed order of worship for a new and unusual one, and more so because of the fickle and fastidious spirits who rush in like unclean swine without faith or reason, and who delight only in novelty and tire of it as quickly, when it has worn off. Such people are a nuisance even in other affairs, but in spiritual matters, they are absolutely unbearable. Nonetheless, at the risk of bursting with anger, I must bear with them, unless I want to let the gospel itself be denied to the people.

Martin Luther
An Order of Mass and Communion for the Church at Wittenberg