Hi, Lucky,
This is really quite an amazing balancing act you have presented to us - claiming …been said.
A person gets an idea - really does not make any difference what it is …oooooooooh, how …possibly, even resolving it.
The honest scholar looks for every credible … item.
Once the data has … a meaningful criteria.
Personally, … been proven.
Then you publish your results - …actually agree…) and there is an honest discussion.
Admittedly, such a … more light then heat on this topic.
But, there is another option - and, this certainly would be acceptable with me…

… desert of unsubtantiated opinion into the lush garden of thoughtful exchange.
God bless
Hey
There are groups of Christians that was not in the Roman Empire after 300 ad.
There are good records that they kept Sabbath until the 1800, 1900’s. More than 15 centuries.
Here is how I do research.
I assume that Sunday is to be kept in the Bible, then I go and try to prove it.
I take all the verses that mentions the first day of the week, Sunday.
Then:
I assume that Sabbath is to be kept in the Bible, then I go and try to prove it.
I take all the verses that mentions the seventh day of the week, Sabbath.
I put them next to each other and then make a conclusion.
This topic Sunday and Sabbath I have researched for around 2 years.
I have debated Protestants about this, and I got the same respond on this forum.
The 9 times the first day is mentioned, they quote it out of context.
They apply the wrongs things about the wrong law.
Ceremonial law, Moral law, Catholic law.
The Sabbath is mentioned easily more than 150 times.
It seems everything I post here most of the people here will try to attack me for some reason.
I thought all Catholics are united in that the Catholic Church changed the day from Sabbath to Sunday. I even quoted the Catholic Mirror.
And I thought James Cardinal Gibbons was a good source:
en.wikipedia.org/wiki/James_Gibbons
Sabbath Day / Sunday Commentary
Main article: Lord’s Day
James Cardinal Gibbons stated “You may read the Bible from Genesis to Revelation, and you will not find a single line authorizing the sanctification of Sunday. The Scriptures enforce the religious observance of Saturday, a day which we never sanctify."[1] Sunday is implicit only in that it is the day of the Lord’s resurrection, and was quickly honored as such by the earliest Christians,[2] as it was never made explicit in the pages of Scripture: “For example, nowhere in the Bible do we find that Christ or the Apostles ordered that the Sabbath be changed from Saturday to Sunday. We have the commandment of God given to Moses to keep holy the Sabbath day, that is the 7th day of the week, Saturday. Today most Christians keep Sunday because it has been revealed to us by the Church outside the Bible.”[3] As it was the first day of the week and the day of the Resurrection, it symbolized the New Life in Christ. According to the Catholic Church and virtually all other Christian denominations - Protestant, Orthodox, and Catholic - the ritual elements of the Mosaic law, such as observance of Sabbath or dietary laws, were abrogated by the coming of Christ and the New Covenant; St Thomas Aquinas went so far as to say practicing ritual elements of the Mosaic law was a mortal sin, as it was tantamount to denying that the Messiah had come.[4]
1 James Cardinal Gibbons, The Faith of Our Fathers (1917 edition), p. 72-73 (16th Edition, p 111; 88th Edition, p. 89).
2 Pliny’s Epistle to Trajan
3 Catholic Virginian, October 3, 1947, p. 9, article “To Tell You the Truth.”
4 Aquinas, St Thomas (1981). Summa Theologiae. Christian Classics. pp. 3020.
I think he knew more about this topic than anyone of us.
biblelight.net/keenan.htm
[pg. 174]
Code:
A. The Christian Church has surely a right, which even the Jewish Church possessed.
Q. Where do you find, in the Old Testament, feasts of precept instituted by the synagogue?
A. In the Book of Esther, chap. 9th, and in the last chapter of the Book of Judith.
Q. Have you any other way of proving that the Church has power to institute festivals of precept?
A. Had she not such power, she could not have done that in which all modern religionists agree with her;—she could not have substituted the observance of Sunday the first day of the week, for the observance of Saturday the seventh day, a change for which there is no Scriptural authority.
catholicvirginian.org/
Catholic Virginian Oct. 3, 1947, p. 9, art. “To Tell You the Truth.”
“For example, nowhere in the Bible do we find that Christ or the Apostles ordered that the Sabbath be changed from Saturday to Sunday. We have the commandment of God given to Moses to keep holy the Sabbath day, that is the 7th day of the week, Saturday. Today most Christians keep Sunday because it has been revealed to us by the [Roman Catholic] church outside the Bible.”
amazon.com/Things-Catholics-Are-Asked-About/dp/B002YUYVHC
Martin J. Scott, Things Catholics Are Asked About (1927), p. 136.
“Nowhere in the Bible is it stated that worship should be changed from Saturday to Sunday … Now the Church … instituted, by God’s authority, Sunday as the day of worship. This same Church, by the same divine authority, taught the doctrine of Purgatory long before the Bible was made. We have, therefore, the same authority for Purgatory as we have for Sunday.”
And now most likely I will be attacked for the post I made.
Luke.