First I want to state clearly that I disagree with the notion that Sunday replaces the Sabbath or that any weekly observance on the “first Day of the Week” is Biblically ordained. And that Biblically The Lord’s Day is The Sabbath.
I believe Paulian Christians kept keeping the Sabbath into the 2nd Century and that even in the Fourth Century many Seventh Day Sabbath keeping Christians still saw themselves as Paulian like the Nazarenes.
But this idea that Sunday was chosen because Pagan at Heart Emperors wanted to worship Jesus on a day for Sun Worship is absurd.
Christians well before Nicaea did start doing First day of the Week Observances because they misunderstood certain “first day of the week” references in Paul and Acts.
There was no Seven Day Week among Pre-Christian Greco-Romans, the idea of a Seven Day week with one day in particular as more Holy than the others is inherently Abrahamic no matter which day you choose.
I'm going to copy and Page a Quote from Tacitus at this link, skim down to [4].
“We are told that the seventh day was set aside for rest because this marked the end of their toils. In course of time the seductions of idleness made them devote every seventh year to indolence as well. Others say that this is a mark of respect to Saturn, either because they owe the basic principles of their religion to the Idaei, who, we are told, were expelled in the company of Saturn and became the founders of the Jewish race, or because, among the seven stars that rule mankind, the one that describes the highest orbit and exerts the greatest influence is Saturn. A further argument is that most of the heavenly bodies complete their path and revolutions in multiples of seven.”
First of all we see a hint that the very idea of a day of rest was revolting to Roman Pagans, this is all the more reason why I believe Capitalist “Work Ethic” Values are Roman in Origin not Protestant.
When at some point Christianized Greco-Romans started identifying the days of the weeks with the visible wandering heavenly bodies since there were seven of them, Saturday was named for Saturn probably because of the influence of what Tacitus said here, or the older sources he got these ideas from.
Now Biblically we know from Amos 5:26 and Acts 7:43 that the Israelites were departing from the proper worship of YHWH when they worshiped the planet we now call Saturn. But there would have been a pagan affiliation no matter which Planet was assigned to the Seventh Day, Saturn’s Harvesting and Agriculture characteristics do fit some of the Sabbath associations. And Tacitus’s observation that Saturn is the farthest from us of the visible Planets is worthy of note. It appearing to move through the night sky the slowest could be a good reason to associate it with rest.
The day on which Jesus Rose from the Dead was associated with The Sun because of the Biblical reasons for viewing The Sun as a symbol of Jesus (Malachi 4:2) and Sunrise as a Symbol of Resurrection (Matthew 28:1, Mark 16:2, Luke 1:78-79, Matthew 4:16, Matthew 5:45, 2 Peter 1:19, 2 Samuel 23:4, Psalm 110:3).
And the SDA belief that it's specifically about attacking the Sabbath is also silly. The fact is none of the earliest Christian Sunday observance based laws even post Nicaea forbid also resting on the Sabbath. And if you wanted to make another day the day of rest with the intention of making Sabbath observance more difficult, what would make sense is making the Sixth Day, the Biblical Preparation Day, the legally enforced day or rest.
