Tafsiran Kejadian 1:6: Rashi, Chizkuni, Rashbam & Ibn Ezra

יהי רקיע BE THERE AN EXPANSE — Let the expansion become fixed; for although the heavens were created on the first day, they were still in a fluid form, and they became solidified only on the second day at the dread command (literally, rebuke) of the Holy One, blessed be He, when he said “Let the firmament be stable” (Genesis Rabbah 4:2). It is to this that allusion is made in what is written in (Job 26:11): “The pillars of heaven were trembling” (i. e. they were unstable) — this was during the whole of the first day — and on the second (Job 26:11): “they were astonished at His rebuke”, like a man who stands immovable, amazed at the rebuke of one who terrifies him.

יהי רקיע בתוך המים, “let there be a horizon in the midst of the waters.” The heaven of which the Torah spoke as being part of G-d’s creative activity on the first “day,” had been an enclave within the waters which had covered the entire “universe” at that time. This paragraph therefore is closely associated with the previous one, i.e. to what had happened on the first “day.” The proof of this lies in the sentence that G-d had created heaven and earth, which makes it clear that both had been created on the first “day. (Compare Genesis 2,4, where the Torah refers specifically to the horizon having been created on the same day as heaven and earth).

ויאמר אלוקים יהי רקיע, after the first day had been concluded with its morning, G’d issued a new directive.