In the 5th century, Socrates Scholasticus Church History book 5 states the fact that until Constantine imposed Dies Solis (Sungod Day) on humanity, most assemblies and believers across the world at that time still kept The Sabbath even as late as 5 centuries later after Yahshua! He clearly knew that this “Sunday” worship was based in Rome on “the account of some ancient tradition”!
"Nor is there less variation in regard to religious assemblies. For although almost all churches throughout the world celebrate the sacred mysteries on the Sabbath of every week, yet the Christians of Alexandria and at Rome, on account of some ancient tradition, have ceased to do this."
Of course, Socrates Scholasticus doesn't actually say what you claim concerning Sunday. Further, the quote you provided, ripped entirely from its context, might seem to suggest that Christians gathered for worship on Saturday (apparently, as opposed to Sunday?) but of course such a reading of Socrates Scholasticus here would require that we either conclude that he doesn't know what he's talking about; as the evidence that Christians gathered on the first day of the week is abundant in the early fathers. However, given the context of the isolated quote, I suspect the more likely situation is that you have misunderstood what he means.
First, let us establish what the ancient fathers themselves have to say (this is hardly exhaustive, but is sufficient to establish the point):
"
If, therefore, those who were brought up in the ancient order of things have come to the possession of a new hope, no longer observing the Sabbath, but living in the observance of the Lord's Day, on which also our life has sprung up again by Him and by His death — whom some deny, by which mystery we have obtained faith, and therefore endure, that we may be found the disciples of Jesus Christ, our only Master — how shall we be able to live apart from Him, whose disciples the prophets themselves in the Spirit did wait for Him as their Teacher? And therefore He whom they rightly waited for, having come, raised them from the dead." - St. Ignatius of Antioch, Epistle to the Magnesians, ch. 9
"
The Sabbath is mentioned at the beginning of the creation [thus]: "And God made in six days the works of His hands, and made an end on the seventh day, and rested on it, and sanctified it." Attend, my children, to the meaning of this expression, "He finished in six days." This implies that the Lord will finish all things in six thousand years, for a day is with Him a thousand years. And He Himself testifies, saying, "Behold, today will be as a thousand years." Therefore, my children, in six days, that is, in six thousand years, all things will be finished. "And He rested on the seventh day." This means: when His Son, coming [again], shall destroy the time of the wicked man, and judge the ungodly, and change the-sun, and the moon, and the stars, then shall He truly rest on the seventh day. Moreover, He says, "You shall sanctify it with pure hands and a pure heart." If, therefore, any one can now sanctify the day which God has sanctified, except he is pure in heart in all things, we are deceived. Behold, therefore: certainly then one properly resting sanctifies it, when we ourselves, having received the promise, wickedness no longer existing, and all things having been made new by the Lord, shall be able to work righteousness. Then we shall be able to sanctify it, having been first sanctified ourselves. Further, He says to them, "Your new moons and your Sabbath I cannot endure." You perceive how He speaks: Your present Sabbaths are not acceptable to Me, but that is which I have made, [namely this,] when, giving rest to all things, I shall make a beginning of the eighth day, that is, a beginning of another world. Wherefore, also, we keep the eighth day with joyfulness, the day also on which Jesus rose again from the dead. And when He had manifested Himself, He ascended into the heavens." - Epistle of Barnabas, ch. 15:3-9
"But Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Saviour on the same day rose from the dead. For He was crucified on the day before that of Saturn (Saturday); and on the day after that of Saturn, which is the day of the Sun, having appeared to His apostles and disciples, He taught them these things, which we have submitted to you also for your consideration." - St. Justin Martyr, First Apology, ch. 67
"
This sixth day is called parasceve, that is to say, the preparation of the kingdom. For He perfected Adam, whom He made after His image and likeness. But for this reason He completed His works before He created angels and fashioned man, lest perchance they should falsely assert that they had been His helpers. On this day also, on account of the passion of the Lord Jesus Christ, we make either a station to God, or a fast. On the seventh day He rested from all His works, and blessed it, and sanctified it. On the former day we are accustomed to fast rigorously, that on the Lord's day we may go forth to our bread with giving of thanks. And let the parasceve become a rigorous fast, lest we should appear to observe any Sabbath with the Jews," - Victorinus, On the Creation of the World
"
If any one should assert that all those who have enjoyed the testimony of righteousness, from Abraham himself back to the first man, were Christians in fact if not in name, he would not go beyond the truth. For that which the name indicates, that the Christian man, through the knowledge and the teaching of Christ, is distinguished for temperance and righteousness, for patience in life and manly virtue, and for a profession of piety toward the one and only God over all — all that was zealously practiced by them not less than by us.
They did not care about circumcision of the body, neither do we. They did not care about observing Sabbaths, nor do we. They did not avoid certain kinds of food, neither did they regard the other distinctions which Moses first delivered to their posterity to be observed as symbols; nor do Christians of the present day do such things. But they also clearly knew the very Christ of God; for it has already been shown that he appeared unto Abraham, that he imparted revelations to Isaac, that he talked with Jacob, that he held converse with Moses and with the prophets that came after." - Eusebius of Caesarea, Church History, Book I, ch. 4.6-8
Now having established the testimony of the first four centuries of Christ's Church, let us turn our attention to the passage from Socrates Scholasticus' History:
"
Moreover the Quartodecimans affirm that the observance of the fourteenth day was delivered to them by the apostle John: while the Romans and those in the Western parts assure us that their usage originated with the apostles Peter and Paul. Neither of these parties however can produce any written testimony in confirmation of what they assert. But that the time of keeping Easter in various places is dependent on usage, I infer from this, that those who agree in faith, differ among themselves on questions of usage. And it will not perhaps be unseasonable to notice here the diversity of customs in the churches. The fasts before Easter will be found to be differently observed among different people. Those at Rome fast three successive weeks before Easter, excepting Saturdays and Sundays. Those in Illyrica and all over Greece and Alexandria observe a fast of six weeks, which they term 'The forty days' fast.' Others commencing their fast from the seventh week before Easter, and fasting three five days only, and that at intervals, yet call that time 'The forty days' fast.' It is indeed surprising to me that thus differing in the number of days, they should both give it one common appellation; but some assign one reason for it, and others another, according to their several fancies. One can see also a disagreement about the manner of abstinence from food, as well as about the number of days. Some wholly abstain from things that have life: others feed on fish only of all living creatures: many together with fish, eat fowl also, saying that according to Moses, these were likewise made out of the waters. Some abstain from eggs, and all kinds of fruits: others partake of dry bread only; still others eat not even this: while others having fasted till the ninth hour, afterwards take any sort of food without distinction. And among various nations there are other usages, for which innumerable reasons are assigned. Since however no one can produce a written command as an authority, it is evident that the apostles left each one to his own free will in the matter, to the end that each might perform what is good not by constraint or necessity. Such is the difference in the churches on the subject of fasts. Nor is there less variation in regard to religious assemblies. For although almost all churches throughout the world celebrate the sacred mysteries on the sabbath of every week, yet the Christians of Alexandria and at Rome, on account of some ancient tradition, have ceased to do this. The Egyptians in the neighborhood of Alexandria, and the inhabitants of Thebaïs, hold their religious assemblies on the sabbath, but do not participate of the mysteries in the manner usual among Christians in general: for after having eaten and satisfied themselves with food of all kinds, in the evening making their offerings they partake of the mysteries. At Alexandria again, on the Wednesday in Passion week and on Good Friday, the scriptures are read, and the doctors expound them; and all the usual services are performed in their assemblies, except the celebration of the mysteries. This practice in Alexandria is of great antiquity," - Socrates Scholasticus, Church History, Book V, ch. 22
I have taken a larger section of the text, but not the entirety of it, for the sake of brevity, however the entirety of the text can be read online (
here) so as to verify my remarks concerning it following.
What should be immediately observable is that here Socrates speaks of diversity of practice concerning the celebration of the Paschal Feast (i.e. Easter), and in the portion which you have quoted (which I have highlighted in bold above) is found in that portion of text in which Socrates discusses the many different ways in which the Lenten Fast is honored.
The indication would seem to be that during the period of Lent it was the common practice in many places for the Church to assemble and celebrate the Word and Sacraments on the sabbath, though this practice had ceased to be observed in the Churches of Alexandria and Rome.
Let us note therefore:
That at no point is there a claim that "until Constantine" Christians gathered on the Sabbath for worship, especially as opposed to on the first day of the week, i.e. the Lord's Day.
But rather, Socrates, in speaking of the period of the Lenten Fast, notes that assembling on the sabbath was custom for most of the churches, save for those in Rome and Alexandria.
This practice can still be observed in the way in which, during Great Lent, the Eastern Orthodox Church observes Saturdays with special significance. Likewise in the Coptic Church the Lenten period includes the forbidding of strict fasting on both Saturdays and Sundays (not unlike in the Western Church which in which Sundays are non-fast days during the Lenten Fast).
What we, therefore, see is that Scholasticus discusses the diversity of practice concerning the celebration of the Paschal Feast, and of the period of fasting prior to it. It is this period of fasting in which the question of assembly on sabbaths takes place; and has nothing to do with the ordinary gathering on the first day of the week, which is not excluded during the Lenten period.
-CryptoLutheran