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

"As for the Saturday, that retained its wonted
credit in the eastern churches, little inferior to the
Lord’s Day, if not plainly equal; not as a Sabbath,
think not so; but as a day designed unto sacred
meetings."[50]
There is no doubt that, after the great flood of
worldliness which entered the church at the time of
Constantine's pretended conversion, and after all
that was done by himself and by Sylvester in behalf
of Sunday, the observance of the Sabbath became,
with many, only a nominal thing. But the action of
the council of Laodicea, to which we shall
presently come, proves conclusively that the
Sabbath was still observed, not simply as a festival,
as Heylyn would have it, but as a day of abstinence
from labor, as enjoined in the commandment. The
work of Constantine, however, marks an epoch in
the history of the Sabbath and of Sunday.
Constantine was hostile to the Sabbath, and his
influence told powerfully against it with all those
who sought worldly advancement. The historian
Eusebius was the special friend and eulogist of
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