Zohar 2:43b

Jewish Mysticism
“Hear oh Israel, YHWH, our Lord, YHWH [is one]” (Deut. 6-4), thus, all is one. On this He is called One. These are three names. How can they be called one? Even though we call them one, how can they be one? Rather, in the vision of the holy spirit it is known, and these in the vision of the closed eye, to know that these three are one. And this is the mystery of the voice as it sounds. A voice is one, and it is three aspects- fire, spirit, and water, and all of them are one in the mystery of the voice. So too, “YHWH, our Lord, YHWH,” these are one. Three aspects, and they are one. This is the voice that a man produces in the unification, to draw his desire in unification from ein sof until the end of all, with this voice that is made with these three that are one. This is the daily unification that is revealed in the mystery of the holy spirit. And several aspects of unification are aroused, and all of them are true. One who performs this, performs, and one who performs this, performs. But this unification that we arouse from below in the mystery of the voice that is one, this is the clarification of the thing in principle.

Translated by Hartley Lachter