In researching this more extensively I came upon
some information that should be helpful. I will post it below.
" Sunday Is the Christian Sabbath
The disciples of Moses teach that the sabbath was changed from Saturday to Sunday by Constantine in 321 A.D., and by the Catholic Church in 364 A.D. The following facts from history prove they are wrong:
1. The Encyclopedia Britannica under "Sabbath" and "Sunday" says. "In the early Christian Church Jewish Christians continued to keep the sabbath, like other points of the law ... On the other hand, Paul from the first days of Gentile Christianity, laid it down definitely that the Jewish sabbath was not binding on Christians. Controversy with Judaizers led in process of time to direct condemnation of those who still kept the Jewish day ... In 321 A.D. Constantine made the Christian sabbath, Sunday, the rest day for the Roman Empire, but it was observed by Christians for nearly 300 years before it became law by Constantine."
2. The New International Encyclopedia on "Sunday" says, "For some time after the foundation of the Christian Church the converts from Judaism still observed the Jewish sabbath to a greater or lesser extent, at first, it would seem, concurrently with the celebration of the first day; but before the end of the apostolic period, Sunday, known as the Lord's day, had thoroughly established itself as the special day to be sanctified (set apart) by rest from secular labor and by public worship. The hallowing of Sunday appears incontestably as a definite law in the Church by the beginning of the fourth century; and the Emperor Constantine confirmed the custom by a law of the state."
3. The Catholic Encyclopedia on "Sunday" says, "Sunday was the first day of the week according to the Jewish method of reckoning, but for Christians it began to take the place of the Jewish sabbath in apostolic times as the day set apart for public and solemn worship of God." This volume quotes a number of early Christian writings of the first, second, and third centuries to prove that Sunday was kept by Christians from the earliest times.
4. The International Standard Bible Encyclopedia on "The Lord's Day" says, "The Lord's day in the New Testament occurs only in Rev. 1:10, but in post-apostolic literature we have the following references: the Epistle of Ignatius to the Magnesians, IX, 1, `No longer keeping the sabbath but living according to the Lord's day, on which also our light arose ... Acts 2:46 represents the special worship as Daily. But this could not continue long ... A choice of a special day must have become necessary, and this day would, of course, have been Sunday ... Uncircumcised Gentiles, however, were free from any obligation of sabbath observance' ... No observance of a special day of rest is contained among the necessary things of Acts 15:28,29 .... A given day as a matter of divine obligation is denounced by Paul as forsaking Christ (Galatians 4:10), and sabbath-keeping is condemned explicitly in Col. 2:16. As a matter of individual devotion to be sure, a man might do as he pleased (Romans 14:5,6), but no general rule as necessary for salvation could be compatible with liberty wherewith Christ has made us free (Galatians 2:1-21; Galatians 3:1-14; Galatians 5:1-4,13)."
5. We next quote from the ten volumes called, "The Ante-Nicene Fathers," the writings of the early church fathers down to A.D. 325 and before Constantine and the Catholic Church are supposed to have changed the sabbath from Saturday to Sunday:
(1) Ignatius, Bishop of Antioch, who lived at the time of the apostles, 30-107 A.D. He, like Polycarp, was a disciple of John and one who should know Christian practice among the early Christians as to the sabbath. He wrote, "And after the observance of the sabbath (that the Jews kept), let every friend of Christ keep the Lord's day as a festival, the resurrection day, the queen and chief of all days of the week ... on which our life sprang up again, and victory over death was obtained in Christ ... it is absurd to speak of Jesus Christ with the tongue, and to cherish in the mind a Judaism which has come to an end .... If any man preach the Jewish law unto you, listen not to him. For it is better to hearken to Christian doctrine from a man who is circumcised, than to a Judaism from one uncircumcised" (Vol. 1, pages 63-82).
(2) In the Epistle of Barnabas, ascribed to Paul's companion by Clement, Origen, and others, we read, "He says to them. `Your new moons and your sabbaths I cannot endure' (Isaiah 1:13). Ye perceive how He speaks: Your present sabbaths are not acceptable go me ... I will 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 on which Jesus rose again from the dead" (Vol. 1, Page 147).
(3) Justin Martyr, a Gentile born near Jacob's well about 110 A.D. writes, "And on the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read ... But Sunday is the day on which we 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 Savior on the same day rose from the dead" (Vol. 1, Page 186). In his dialogue with Trypho, a Jew, Justin Martyr says, "Is there any other matter, my friends, in which we are blamed, than this, that we live not according to the law, and are not circumcised in the flesh as your forefathers were, and do not observe the sabbaths as you do? ... Christians would observe the law, if they did not know why it was instituted .... For we too would observe the fleshly circumcision, and the sabbaths, and in short all feasts, if we did not know for what reason they were enjoined you .... How is it, Trypho, that we would not observe those rites which do not harm usI speak of fleshly circumcision, and sabbaths, and feasts? ... The Gentiles, who have believed in Him, and who have repented of their sins ... shall receive the inheritance along with the patriarchs ... even although they neither keep the sabbath, nor are circumcised, nor observe the feasts .... Christ is useless to those who observe the law .... The sabbath and sacrifices and offerings and feasts ... have come to an end in Him who was born of a virgin .... But if some, through weakmindedness, wish to observe such institutions as were given to Moses ... along with their hope in Christ ... they shall probably be saved" (Vol. 1, Pages 199-218).
(4) Tertullian, presbyter of the North African Church, who was born about 145 A.D., writes, "The Holy Spirit upbraids the Jews for their holydays. Your sabbaths, and new moons, and ceremonies my soul hateth .... By us (Christians), to whom sabbaths are strange ... to the heathen each festive day occurs but once annually: you (Christians) have a festive day every eighth day .... Others 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 ... you who reproach us with the sun and Sunday should consider your own proximity to us. We are not far off from your Saturn and your days of rest .... It follows, accordingly, that, in so far as the abolition of carnal circumcision and of the old law is demonstrated as having been consummated at its specific times, so also the observance of the sabbath is demonstrated to have been temporary" (Vol. III, Pages 70, 123, 155, 313-14).
(5) In "The Teachings of the Twelve Apostles," written about 80 A.D., we read, "But every Lord's day (Sunday) do ye gather yourselves together, and break bread and give thanksgiving" (Vol. VII, Page 381).
(6) In the Constitutions of the Holy Apostles (2nd century) we read, "Break your fast ... the first day of the week, which is the Lord's day ... After eight days let there be another feast observed with honor, the eighth day itself" (Vol. VII, Page 447).
(7) In "The Teachings of the Apostles," written 105 A.D., we read, "The apostles therefore appointed: ... on the first day of the week let there be service and reading of the Scriptures, and the oblation (Lord's Holy Supper): because on the first day of the week our Lord arose upon the world, and ascended to heaven" (Vol. VIII, Page 668).
(8) Irenaeus, 178 A.D., in arguing that the Jewish sabbaths were signs and types and were not to be kept since the reality of which they were shadows had come, says, "The mystery of the Lord's resurrection may not be celebrated on any other day than the Lord's day and on this alone should we observe the breaking of the Paschal Feast ... Pentecost fell on the first day of the week, and was therefore associated with the Lord's day."
(9) Clement of Alexandria, 174 A.D., says, "The old seventh day has become nothing more than a working day."
(10) Theophilus, pastor of Antioch, 162 A.D., says, "Both custom and reason challenge us that we should honor the Lord's day, seeing on that day it was that our Lord completed His resurrection from the dead."
(11) Origen, about 200 A.D., says, "John the Baptist was born to make ready a people for the Lord, a people for Him at the end of the covenant now grown old, which is the end of the sabbath ... It is one of the marks of a perfect Christian to keep the Lord's day."
(12) Victorianus, 300 A.D., says, "On the Lord's day we go forth to our bread and giving thanks. Lest we should appear to observe any sabbath with the Jews, which Christ Himself the Lord of the sabbath in His body abolished" (Section 4, "On the Creation").
6. Eusebius, the Father of Church History, who made a history of the time between the birth of Christ and Constantine, and who lived 265-340 A.D., says, "From the beginning Christians assembled on the first day of the week, called by them the Lord's Day, for the purpose of religious worship, to read the Scriptures, to preach and to celebrate the Lord's Supper ... the first day of the week on which the Savior obtained the victory over death. Therefore, it has the preeminence, first in rank, and is more honorable than the Jewish Sabbath."
Hope this helps