Част 16 · Chapter 140

And the answer to this is that the essential couplings are only the two mentioned above. And the matter is that before Adam HaRishon came, and before the creation of the world, ZON were back to back. Therefore all the worlds were back to back, in the secret of Assiya, which is back to back. Therefore the thirty-nine labors (Melachot) are in the secret of Assiya, for there is the action (Ma'aseh); and they were all in the secret of back to back.