Judaism
Christianity was originally a sect of Second Temple Judaism, but the two religions diverged in the first century. The differences between Christianity and Judaism originally centered on whether Jesus was the Jewish Messiah but eventually became irreconcilable. Major differences between the two faiths include the nature of the Messiah, of atonement and sin, the status of God's commandments to Israel, and perhaps most significantly of the nature of God himself. Due to these differences, Judaism traditionally regards Christianity as Shituf or worship of the God of Israel which is not monotheistic. Christianity has traditionally regarded Judaism as obsolete with the invention of Christianity and Jews as a people replaced by the Church, though a Christian belief in dual-covenant theology emerged as a phenomenon following Christian reflection on how their theology influenced the Nazi Holocaust.
Hasideans
Scholars have until recently started with the assumption that Hellenism "took root only in the upper classes of society, the main body of the [Jewish] nation being wholly untouched by it" and distinguished between the pious, law-abiding majority of the people and the Hasideans as a society of "extra-pious" Jews. However, the sources mentioned do not justify such a view. The συναγωγ σιδαίων of the books of the Maccabees, upon which so much emphasis is laid, corresponds, as has already long been known, to the קהל חסידים of the Psalms, which means neither "sect" nor "society", but only "congregation", with no idea of party. The piety attributed to Ḥasidim in the Talmudic sources is not in any way suggestive of a sect (Lehmann, in "R. E. J." xxx. 182 et seq.). The supposition that they were a sect closely associated with the scribes, and related to them, rests only on the fact that the two classes are mentioned together in I Macc. vii. 12, 13; the genuineness of verse 13, however, has been questioned by Hitzig ("Gesch. des Volkes Israel," p. 417).