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

Sabbath-keeping church of Thessalonica, who in
turn patterned after the churches in Judea.
The first churches were founded in the land of
Judea. All their members had from childhood been
familiar with the law of God, and well understood
the precept, "Remember the Sabbath day, to keep it
holy." Besides this precept, all these churches had a
peculiar memento of the Sabbath. They knew from
our Lord himself that the time was coming when
they must all suddenly flee from that land. And in
view of this fact, they were to pray that the moment
of their sudden flight might not be upon the
Sabbath; a prayer which was designed, as we have
seen, to preserve the sacredness of the Sabbath.
That the churches in Judea were composed of
Sabbath-keeping members, admits therefore of no
doubt.
Of the churches founded outside the land of
Judea, whose origin is given in the book of Acts,
nearly all began with Jewish converts. These were
Sabbath-keepers when they received the gospel.
Among these, the Gentile converts were engrafted.
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