Editing Merkavah (Divine Chariot) (section)

==== Beriah ====
The concept of the Merkavot of the worlds of BY"A is that the Shechinah, Malchut of Atzilut, does not descend below to the worlds of BY"A except through the Merkavah, even to prophets like Isaiah and Ezekiel, except that one saw the Merkavah of Beriah, and the other saw the Merkavah of Yetzirah. And all the descents of Malchut of Atzilut downward, and all its ascents, are all through the Merkavah.

Isaiah perceived the Merkavah of Beriah, and therefore saw "Hashem Tzeva'ot sitting on a high and lofty throne, and Seraphim standing above Him," and the Seraphim of the world of Beriah say "Holy, Holy, Holy," which is the concept of Keter Malchut of Beriah.