Fifty Gates of Wisdom
Fifty Gates of Wisdom (Kab.). The number is a blind, and there are really 49 gates, for Moses, than whom the Jewish world has no higher adept, reached, according to the Kabbalas, and passed only the 49th. These “gates” typify the different planes of Being or Ens. They are thus the “gates” of Life and the “gates” of understanding or degrees of occult knowledge. These 49 (or 50) gates correspond to the seven gates in the seven caves of Initiation into the Mysteries of Mithra (see Celsus and Kircher). ‘I’he division of the 50 gates into five chief gates, each including ten—is again a blind. It is in the fourth gate of these five, from which begins, ending at the tenth, the world of Planets, thus making seven, corresponding to the seven lower Sephiroth—that the key to their meaning lies hidden. They are also called the “gates of Binah” or understanding.
Source: H.P.Blavatsky - The Theosophical Glossary