Constantine the Great, emperor of Rome during much of the first half of the 4th Century AD, attributed his success as a military leader and ruler to his faith in the Christian God. He was the first Roman emperor to profess Christianity, and subsequently codified certain Christian traditions as Roman law. One of these traditions was the celebration of the Sabbath on Sunday. In AD 321, the emperor decreed, "On the venerable day of the Sun [Sunday] let the magistrates and people residing in cities rest, and let all workshops be closed" (Codex Justinianus lib. 3, tit. 12, 3; trans. in Philip Schaff, History of the Christian Church, Vol. 3, p. 380, note 1).
Did Constantine change the Sabbath? Did Constantine make the Sabbath Sunday instead of Saturday?
Although Constantine officially established a Sunday Sabbath as Roman law, the New Testament records Christians celebrating the Sabbath on Sunday within probably 20—40 years of Jesus' death. Acts 20:7 says that when Paul and his companions were in Troas, a city in Macedonia, it was "On the first day of the week, when we were gathered together to break bread" [i.e. celebrate the Lord's Supper]. Paul also instructed the Corinthians that "On the first day of every week, each of you is to put something aside and store it up, as he may prosper, so that there will be no collecting when I come" (1 Corinthians 16:2). Apparently, the Christian church was already gathering together on Sundays long before Constantine. So, no, Constantine simply codified what was already a standard Christian practice.
Is Sabbath-keeping something Christians should do?
Is the Sabbath Saturday or Sunday?
What is the Sabbath? Is the Sabbath day for rest or for worship?
Is church attendance important?
Are Christians expected to obey the Old Testament law?
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