Early Church Fathers on Sunday vs. the Sabbath . . .

Some Sabbatarian groups such as Seventh Day Adventists insist that most Christians have abandoned the Commandment, “Keep Holy the Sabbath.”  They refuse to accept the Bible verses like Acts 20:7, 1 Cor. 16:2 and Col. 2:16 which speak of the Sabbath of the New Covenant being transferred to the day on which our Lord rose from the dead (Sunday).  They also reject the practices of the Early Church Fathers (ECFs) who carried on this Apostolic Tradition.

The Didache (Teachings of the Twelve Apostles) - But every Lord's day . . . gather yourselves together and break bread, and give thanksgiving after having confessed your transgressions, that your sacrifice may be pure. But let no one that is at variance with his fellow come together with you until they be reconciled, that your sacrifice may not be profaned (Didache 14 [A.D. 70]).

Ignatius of Antioch - [T]hose who were brought up in the ancient order of things [i.e., Jews] 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 (Letter to the Magnesians 8 [A.D. 110]).

The Didascalia - The Apostles further appointed; On the first day of the week let there be service, and the reading of the holy scriptures, and the oblation [sacrifice of the Mass]. [A.D. 225]).

Eusebius - [T]he day of his [Christ's] light . . . was the day of his resurrection from the dead, which they say, as being the one and only truly holy day and the Lord's day, is better than any number of days as we ordinarily understand them, and better than the days set apart by the Mosaic Law for feasts, new moons, and Sabbaths, which the Apostle [Paul] teaches are the shadow of days and not days in reality (Proof of the Gospel 4:16:186 [A.D. 319]).

Athanasius - The Sabbath was the end of the first creation, the Lord's day was the beginning of the second, in which he renewed and restored the old in the same way as he prescribed that they should formerly observe the Sabbath as a memorial of the end of the first things, so we honor the Lord's day as being the memorial of the new creation (On Sabbath and Circumcision 3 [A.D. 345]).

Cyril of Jerusalem - Fall not away either into the sect of the Samaritans or into Judaism, for Jesus Christ has ransomed you. Stand aloof from all observance of Sabbaths and from calling indifferent meats common or unclean (Catechetical Lectures 4:37 [A.D. 350]).

Council of Laodicea - Christians should not Judaize and should not be idle on the Sabbath, but should work on that day; they should, however, particularly reverence the Lord's Day and, if possible, not work on it, because they were Christians (canon 29 [A.D. 360]).