“When you look into the abyss, the abyss also looks into you” – Nietzsche
The impassible barrier that separates the world of Atziluth from the lower three worlds on the tree of life. This concept is associated with the invisible sephirah Da’at.
In modern Kabbalah there is a well developed notion of an Abyss between the three supernal sephiroth of Kether, Chokhmah, and Binah, and the seven lower sephiroth. When one looks at the progress of the Lightning Flash down the Tree of Life, then one finds that it follows the path structure connecting sephiroth except when it makes the jump from Binah to Chesed, thus reinforcing this idea of a “gap” or “gulf” which has to be crossed.
One of the earliest sources for the Abyss comes from the Bible:
“And the earth was without form, and void; and darkness was upon the face of the deep.”