In the Jewish Kabbalah tradition, Ayn Sof (Ain Sof, Hebrew "boundlessness" or "without end"), also known referred to as Divine Being, is the name for God as he is unknown, or the mysterious and ultimate source of all existence. All other existence flows, or emanates from Ayn Sof.
According to the Zohar, the ten Sefirot (ultimate principles or divine realities) as found in the Adam Kadmon emanate from Ayn Sof.
Theories of the relation between Ayn Sof and all other realities and levels of reality were developed by the Jewish mystical thinkers of the middle ages, such as Isaac the Blind and Azriel who were influenced by concepts of Neoplatonism which they modified to conform to their own leanings.