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 the public and solemn worship of God. The practice of meeting together on the first day of the week for the celebration of the Eucharistic Sacrifice is indicated in Acts 20:7, 1 Corinthians 16:2, Colossians 2:16-17, and Revelation 1:10, it is called the Lord's day. In the Didache (xiv) the injunction is given: "On the Lord's Day come together and break bread. And give thanks (offer the Eucharist), after confessing your sins that your sacrifice may be pure". St. Ignatius (Ep. ad Magnes. ix) speaks of Christians as "no longer observing the Sabbath, but living in the observance of the Lord's Day, on which also Our Life rose again". In the Epistle of Barnabas (xv) we read: "Wherefore, also, we keep the eight day (i.e. the first of the week) with joyfulness, the day also on which Jesus rose again from the dead".
St. Justin is the first Christian writer to call the day Sunday (I Apol., lxvii) in the celebrated passage in which he describes the worship offered by the early Christians on that day to God. The fact that they ment together and offered public worship on Sunday necessitated a certain rest from work on that day. However, Tertullian (202) is the first writer who expressly mentions the Sunday rest: "We, however (just as tradition has taught us), 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" ("De orat.", xxiii; cf. "Ad nation.", I, xiii; "Apolog.", xvi).
These and similar indications show that during the first three centuries practice and tradition had consecrated the Sunday to the public worship of God by the hearing of the Mass and the resting from work. With the opening of the fourth century positive legislation, both ecclesiastical.
by what authority?
By Christ (Matt. 16:19)
The books of Didache,Ignatius,Barnabas,Justin and Tertullian are not in my Bible. Therefore they do not count as the Word of God. As far as Revelation 1:10 referring to The Lords Day, scripturally you are on sinking soil again because Mark 2:28 has Christ declaring the Sabbath as His day. I am looking for verses that emphatically declare that God is declaring the Sabbath is done and over with and let’s go with Sunday from now on with the same unmistakable clarity that the Sabbath observance was declared. And it would have helped if Christ, while He was here on earth, put this “new law” into practice since He is our example. Pretty careless of Him, don’t you think?