Sabbatarian
From BiblePortal Wikipedia
Sabbatarian [1]
(1):
(n.) One who regards and keeps the seventh day of the week as holy, agreeably to the letter of the fourth commandment in the Decalogue.
(2):
(n.) A strict observer of the Sabbath.
(3):
(a.) Of or pertaining to the Sabbath, or the tenets of Sabbatarians.