9th Century Sabbath Keeping in Bulgaria

Pope Nicholas I

"(Pope Nicholas I, in answer to letter from Bogaris, ruling prince of Bulgaria.) "Ques. 6-Bathing is allowed on Sunday. Ques. 10-One is to cease from work on Sunday, but not also on the Sabbath." Hefele, 4,346-352, sec. 478
The Bulgarians had been accustomed to rest on the Sabbath. Pope Nicholas writes against this practice.

Constantinople
(Photuus, Patriarch of Constantinople {in counter- synod that deposed Nicolas}, thus accused Papacy). Against the canons, they induced the Bulgarians to fast on the Sabbath." Photius, vonKard, Hergenrother, 1, 643

Note: The Papacy tried to bring the seventh-day Sabbath into disrepute by insisting that all should fast on that day. In this manner she sought to turn people towards Sunday, the first day, the day that Rome had adopted."
ST
But the seventh day is the sabbath of the LORD thy God: Exodus 20:10