The Assideans (the Anglicized form, derived through the Greekasidaioi, of the HebrewHasidim, "the pious"), were a party or sect which stood out against the Hellenization of the Jews in the 2nd century B.C. After the massacre of those who fled from the forces of Antiochus Epiphanes and would not resist and fight on the day of the Shabbat, Mattathias (or Judas, his son) decided to set aside the law and was joined by a company of Assideans, brave men of Israel every one, who offered themselves willingly for the law (1 Macc. ii. 42, cf. 2 Macc. viii. I).
On the appointment of Alcimus, "a descendant of Aaron" as high-priest, "the Assideans were the first who sought peace" (1 Macc. vii. 13 f.); but the treacherous murder of sixty of them (ib. 16) by Bacchides threw them back into the arms of Judas. According to 2 Macc. xiv., Alcimus identified them with the whole party of the rebels, of which they were only one, though the most important, section.