Shneur Zalman of Liadi quotes
And so the teaching (Torah) was likened to water: like water comes down from a high place to a low place, so the teaching descended from its honorable place, as it is His will and wisdom, and the light of Him that be blessed and thought cannot grasp it at all. From there it went in the secret stairway via the worlds, until it was dressed in material things and matters of this world, which are all the ordinants (mitzvot) and their ways, in combinations of material letters in ink on the book, twenty four books in the Tanakh, so thought will be able to comprehend it, and even speech and act, below the level of thought.
Shneur Zalman of Liadi