Sab·ba·tar·i·an 
(săb′ə-târē-ən)
(săb′ə-târē-ən)n.
1. One who observes Saturday as the Sabbath, as in Judaism.
2. One who believes in strict observance of the Sabbath.
adj.
Relating to the Sabbath or to Sabbatarians.
[From Late Latin sabbatārius, from Latin sabbatum, Sabbath; see SABBATH.]
Sab′ba·tari·an·ism n.