Sforno on Genesis 1:2/ספורנו על בראשית א׳:ב׳

1והארץ היתה תהו ובהו, “this very center which was created at that time was composed of a mixture of raw materials, known as tohu, and its original external appearance is what is described as bohu. The reason is that the whole expanse of tohu was comprised of a uniform appearance. This explained that the first raw material was something entirely new. It is described as tohu to indicate that at that point it was merely something which had potential, the potential not yet having materialised, been converted to something actual. When we read in Samuel I 12,21 כי תהו המה, the meaning is that these phenomena did not exist in reality, they existed only in someone’s imagination. [a reference to pagan deities. Ed.] The appearance of this primordial raw material is described as bohu, meaning that as such it came to exist in actual fact, in real terms. Isaiah 34,11 “weights of emptiness.” This describes any phenomenon that does not retain its appearance for any length of time. It constantly changes like a chameleon.

2וחשך, a reference to the air (atmosphere, totally dark which emanated at that time from the original raw material. על פני תהום, over the expanse of the two basic foundations which also emanated from the same origin and surrounded one another.

3ורוח אלוקים, the energy propelling the planet is called ruach,” as we know from Psalms 104,4 עושה מלאכיו רוחות, “He energises His messengers.”

4מרחפת על פני המים, they activated the atmosphere above the waters which at that time surrounded the earth. This is the reason why the part which was closer to the spherical planet became incandescent through its motion [friction. Ed.] This phenomenon is what we know as the original fire. On the other hand, the part of the energy which remained closer to the waters acquired a degree of frigidity from the proximity to the waters, so that only a small part of the atmosphere really became hot through revolving and giving off sparks of fiery light.