“…the first kabbalistic dualistic system was presented by … Rabbi Isaac ben Jacob ha-Cohen, entitled Treatise on the Emanations on the Left … written in Castile about 1265…(describing) “a parallel system of seven divine evil powers, the first of which is called Samael and the seventh, feminine one is called Lilith … “he was the first to bring them together and present them as a divine couple, parallel to God and the shekhinah, who rule over a diverse structure of evil demons, who struggle for dominion in the universe against the powers of goodness, the emanations on the right … Rabbi Isaac was the first to present a hierarchy of evil powers and evil phenomena, including illnesses and pestilence, connecting all of them in one system.”
“Rabbi Isaac presented a mythological description of the relationship between the satanic powers; he described the “older Lilith” and “younger Lilith,” the latter being the spouse of Asmodeus, whom Samael covets. The realm of evil includes images of dragons and snakes and other threatening monsters.”
“Unlike Rabbi Ezra of Girona, (Rabbi Isaac) …. did not find the root of evil’s existence in the Garden of Eden and human sin. Evil evolved from the third sefirah, binah, as a distorted side effect of the process of emanation. It continues throughout the history of the world, and will come to an end in the final apocalyptic struggle between Samael and the messiah.”
“De Leon even preserved a hint to the title of Rabbi Isaac’s treatise. In the Zohar the realm of evil is called sitra ahra, an Aramaic phrase meaning “the other side.” “Other” is the unmentionable left side, which is also the name of God’s archenemy, Samael.”
–Joseph Dan, Kabbalah: A Very Short Introduction, 2006, pp. 50-3.