Part 11 · Chapter 75

In this too you will understand the matter of Bina, who is also called “the tower flying in the air,” in the secret of “the dissolution of vows flies in the air, and has nothing to rest upon” (Chagigah 10). And the matter is that the Yesod of Arich is in the Bina of ZA, and therefore both the Yesod and the Bina are called by this name.