The Secret Signature of the Letters
“Isaac’s picture of the universe rests, therefore, on the idea that the different realms of Creation, each according to its rank in the hierarchy of things, are in communication with the roots of all being as given in the world of the sefiroth.
The limited powers proceed from the unlimited powers, and the secret signature of the letters acts in everything, but nowhere more clearly than in man. But to the current that flows downward there corresponds another, upward movement.
When Isaac says in his commentary on Yesirah (end of chapter 3) that “all things return to the root of their true being,” he means, in this context, that a thing can act only in that which is related to its principle.
But his disciples already understood expressions of this kind in the sense of a return of all things to God. “Everything issues from the first Cause, and everything returns to the first Cause.”
Such a return can have both an ontological and an eschatological aspect. Even before the end of all things all being seeks to return, in accordance with its nature, to its origin, in the spirit of the ancient philosophical thesis of the appetitus naturalis, which the Neoplatonists above all rendered popular in the Middle Ages.
But also, the eschatological nuance of a “restoration of all things to their original being,” hashabath kol ha-debharim le-haw-wayatham, is not absent among Isaac’s pupils, who probably derived it from him.”
Gershom Scholem, Origins of the Kabbalah, pp. 299-300.