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 Judaism
Judaism has its origins in the Iron Age Kingdom of Judah and in Second Temple Judaism. It has three essential and related elements: study of the written Torah (the books of Genesis, Exodus, Leviticus, Numbers, and Deuteronomy); the recognition of Israel (defined as the descendants of Abraham through his grandson Jacob) as a people elected by God as recipients of the law at Mount Sinai, his chosen people; and the requirement that Israel live in accordance with God's laws as given in the Torah.