Ramban, on Gen 1:7

“And God made a firmament, and divided the waters that were under the firmament, from those that were above the firmament, and it was so.”

“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.”

Imported from an open dataset — not yet checked against the printed edition.