Genèse 1:7

And God made the firmament: He arranged it in its position; and that is its making, as per (Deuteronomy 21:12), "and she made her nails."

From over (me'al) the firmament: It does not state, over (al) the firmament, but rather, from over the firmament; since they are suspended in the air. And why does it not state, "it was good," on the second day? Because the work of the water was not completed until the third day; and behold, He [only] started it on the second [day], and something that is not finished is not in its fullness and goodness. And on the third [day], when the work of the water was completed and He started a different work and completed it, He repeated "it was good" twice on it - one for the finishing of the work of the second [day] and one for the finishing of the work of that day.

And the Lord made the expanse, upbearing it with three fingers, between the confines of the heavens and the waters of the ocean, and separated between the waters which were below the expanse, and the waters which were above, in the collection (or covering) of the expanse; and it was so.

“And He made” – there is distinction employing [the word] bein with lamed. like “between water and water” (bein mayim lamayim) Genesis 1:6, “between holy and profane” (bein kodesh l’chol) Ezekiel 44:23 and there is [distinction] with bein and bein, as here – “and He separate between bein the waters below the firmament and between bein etc.”, and there is [distinction] with both of them, like “between you and between your G-d” (beineichem l’vein e-loheichem). The meaning of “and it was so” is that it attached to what follows: “when that happened, He called the heavens…”

AND G-D MADE THE FIRMAMENT. The word asi’yah (doing) always means adjusting something to its required proportion.

AND IT WAS SO. On the first day, And there was light is written after And G-d said, ‘Let there be light,’ in order to explain that after the command of G-d, it [the light] came forth into actuality and was as He decreed it to be. But here, after the command, Let there be a firmament, it is written, And G-d made the firmament, and divided, etc.; why then has Scripture added here, And it was so? It is to tell us that it was to be ever so, for all times.
But Rabbi Abraham ibn Ezra explained that the expression and it was so is attached to the verse which follows, meaning when it was so, G-d called the firmament Heaven. That is not correct.
In Bereshith Rabbah the Rabbis have said: “And G-d made the firmament. This is one of the verses which Ben Zoma found difficult: And G-d made, etc. But was not [the world created] by command, as it is written, By word of the Eternal were the heavens made?” Now Ben Zoma’s difficulty was not only on account of the word vaya’as (And He made), since on the fourth, fifth, is not found; only vayibra (and He created). and sixth day, vaya’as is also written. Rather, his difficulty was, as I have said, that on the other days, immediately after G-d’s command, it is written, And it was so, indicating that it came into being immediately after the command, but here on the second day, after it says, And G-d said — vaya’as (And He made) is written! This was his question. Perhaps Ben Zoma had some secret interpretation which he did not want to reveal. This is the explanation of the cause of his difficulty.

"And G-d made the firmament" - and it was that when some of the elemental water was removed from under that part of the waters which became vaporous in nature, as it was when He said, "let the waters be gathered from beneath the heavens" Genesis 1:9, it was fit that the vaporous part would descend to that same place from which the that [non-vaporous portion of] waters was removed. But He made it such that that "firmament" that separates would have the power to stop and prevent the vaporous portion from descending - that's the "waters which are above the firmament", such that the transformed atmospheric portion would descend, while the vaporous would remain in its original place. Because of this, when the moist vapor reaches it [i.e., the firmament], it condenses and gives rise to rain, snow and hail. As they condense they descend, as it is said, "at the sound of His placing an abundance of water in the heavens" Jeremiah 10:13. - what it wanted by saying "heavens": the firmament which condenses the atmospheric part [of the waters], as it is said "And G-d called the firmament "heavens" Genesis 1:8. Now when the cloudy, excited vapor arrives there [at the firmament], it generates thunder and lightning, and it is said: "He lifts up clouds from the ends of the earth, thunder from the rain He makes" [continuation of verse quoted previously from Jeremiah]. Now, seeing as how some of the heavier watery element is above the lighter air, which from our perspectives is against their nature - this without doubt indicates the action of an volitional actor, intended such an outcome, as it is said, "the work of His hands shall the firmament declare" Psalms 19:2

"and it was so" - it remained thus against its nature.