“And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.” (Gen 1:7) The verb “separate” is the second term describing the creative work of God. It means not only “to create” but also “to separate” – in Hebrew badal – the created elements. Why?
Separating one thing from another means putting distinctions to make a classification or a diversification. It also means to set boundaries that should not be “trespassed” because they are directly established by God. These borders or boundaries represent the very structure of the cosmos, a term derived from Greek philosophy and present in the Greek translation of the Hebrew Bible, the so called “Septuagint” . The cosmos corresponds to the biblical concept of “creation” and is useful to understand another key term: chaos. Chaos is the lack of boundaries and distinctions and was figured by the ancient authors of the Bible as the deep waters that submerged the earth.
They were the waters of the primordial sea (cfr. Genesis 1,1-2) and the waters that came again to cover the earth during the flood (cfr. Genesis 6-8).
This is not just an imagine, because the concept of “separating” is at the basis of the Jewish laws contained in the Old Testament, including the Ten Commandments (cf. Exodus 20; Deuteronomy 5). Therefore the laws are not simply bans and prohibitions, but boundaries that separate cosmos from chaos. According to the Jews biblical laws were (and are) the reflection on earth of the cosmic order established by God; trespassing biblical laws means to destruct the entire creation.
The “firmament” was a kind of giant “bell jar” that God created in the midst of the primordial waters, so that part of them were raised upward while other ones remained on earth. The first belonged to the so-called “heavenly ocean” which will be called “sky”. The second one was instead the ocean that still covered the earth. Thus was created the planet earth as conceived by the ancients: a gigantic aquatic expanse. The land, in fact, had not yet emerged.