Mastema is the devil’s name in the Jewish Book of Jubilees. He is said to be the chief of the evil spirits and the enemy of righteousness. According to Jubilees, it was Mastema rather than God who tested Abraham and killed the firstborn in the land of Egypt. In Hosea “mastema” means enmity (Hosea 9:7), and the Book of Jubilees the term “the Prince of Mastema” (“the Prince of Enmity”) as well as Mastema as a proper name. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 626