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.
Origins of Rabbinic Judaism
Orthodox Judaism does not accept the scholarly view that Rabbinic Judaism came into being in the post-Second Temple era. Rather, it sees the Judaism of this period as continuing organically from the religious and cultural heritage of the Israelites, stemming from the Revelation at Sinai onwards. According to this view, while the title "Rabbi" was not used earlier, Moses was the first rabbi (and is commonly referred to by Orthodox Jews as "Moses our Rabbi"), with the knowledge and laws received at Sinai being passed down from teachers to students through the era of the Judges, and the prophets (most of whom are seen as the "rabbis" of their time), through the Sages of the late Second Temple period, and continuing until today.