Treatise on the Left Emanation

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The Treatise on the Left Emanation ({{Langx|he|מאמר על האצילות השמאלית|translit=Ma'amar al ha-Atzilut haSimalit}}) is a Kabbalistic text by Rabbi Isaac ben Jacob ha-Cohen, who with his brother Jacob traveled in Spain and Provence in the period of 1260–1280.Arthur Versluis, Magic and Mysticism: an Introduction to Western Esotericism (2007) p. 65: "We must also note the appearance, in the thirteenth century, of the "Treatise on the Left Emanation" by Isaac ha-Kohen, who with his brother Jacob traveled in Spain and Provence in the period of 1260-1280"

Scholars credit this text with being the first to present a "comprehensive concept of evil", bearing a striking resemblance to that found in Gnosticism. It is also the first to treat Samael and Lilith as a couple, likely inspiring later such depictions in the Zohar.{{Cite journal |last=Dan |first=Joseph |date=1980 |title=Samael, Lilith, and the Concept of Evil in Early Kabbalah |url=https://www.jstor.org/stable/1486451 |journal=AJS Review |volume=5 |pages=17–40 |doi=10.1017/S0364009400011831 |jstor=1486451}}

Isaac may be the pseudepigraphic author of other texts including the Pseudo-R. Eleazar Responsum, and the Pseudo-R. Yehushiel Responsa.Mark Verman, The Books of Contemplation: Medieval Jewish Mystical Sources (1992) p. 176