The study of Kabbalah is the engagement with the Jewish mystical tradition, a vast body of esoteric teaching concerning the hidden nature of God, the structure of the spiritual worlds, the meaning beneath the surface of the Torah, and the soul's place in the divine scheme. The word kabbalah means "that which is received," and the tradition presents itself as a received wisdom transmitted across the generations. Its central texts and concepts, above all the medieval Zohar, and the doctrine of the ten sefirot, the emanations through which the infinite and unknowable God, the Ein Sof, unfolds into creation, form the core of its study, later systematised and deepened by the sixteenth-century school of Isaac Luria at Safed, whose teaching on the contraction of God to make room for the world, the shattering of the vessels, and the human task of cosmic repair, tikkun, became enormously influential.
Traditional Judaism has long surrounded the study of Kabbalah with cautions, holding it a dangerous and demanding wisdom not to be approached lightly. A widely cited restriction held that its deepest study should be reserved for mature, learned and married men of at least forty years, well grounded first in the Torah and Talmud, lest the powerful and easily misunderstood teachings mislead the unprepared. The tradition was cultivated within Judaism, shaping Jewish law, liturgy and especially the Hasidic movement, and was closely guarded. In the modern era Kabbalah has also been taken up far beyond its traditional Jewish setting: adapted into the "Hermetic Qabalah" of Western ceremonial magic, and popularised in recent decades by movements that teach a form of it to a wide, often non-Jewish audience, developments that many within traditional Judaism regard as detaching the teaching from the observant Jewish life and learning that they hold to be its indispensable ground.