History of the Sabbath and First Day of the Week - John N. Andrews

divine precept or apostolic example. His principal
point was that they had as good a right to do it as
the heathen had. One hundred and twenty one years
after Tertullian, Constantine, while yet a heathen,
put forth his famous edict in behalf of the heathen
festival of the sun, which day he pronounced
"venerable." And this heathen law caused the day
to be observed everywhere throughout the Roman
Empire, and firmly established it both in Church
and State. It is certain, therefore, that at the time of
its entrance into the Christian church, Sunday was
an ancient weekly festival of the heathen world.
That this heathen festival was upon the day of
Christ's resurrection doubtless powerfully
contributed to aid "patriotism" and "expediency" in
transforming it into the Lord’s Day or Christian
Sabbath. For, with pious motives, as we may
reasonably conclude, the professed people of God
early paid a voluntary regard to several days,
memorable in the history of the Redeemer.
Mosheim, whose testimony in behalf of Sunday
has been presented already, uses the following
language relative to the crucifixion day:--
448