Kabbalah קבלה
The inner, hidden teaching of the Torah: the sefirot, the concealed structure of worlds and the meaning of the commandments.
Kabbalah comes from lekabel, «to receive»: a teaching transmitted from master to student rather than in public. The Mishna restricts it explicitly, and the Talmud tells of four who entered the «orchard», of whom only Rabbi Akiva emerged unharmed.
Its principal texts are Sefer Yetzirah, on creation through letters and numbers, and the Zohar, published in Spain in the thirteenth century. Its key terms: the ten sefirot, stages through which the infinite becomes approachable; Ein Sof; the Shechina, which goes into exile with the people.
The turning point came in Tzfat: in the sixteenth century the Arizal gave a system in which creation begins with tzimtzum, a self-contraction, continues through the shattering of the vessels, and in which all of history is tikkun, repair. From this grew the idea that every mitzva has cosmic effect — and, in time, hasidism.