Commentary for Genesis 1:8

ויקרא אלהים לרקיע שמים AND GOD CALLED THE EXPANSE HEAVEN — The word “שמים”, Heaven, may be regarded as made up of שא מים “Carry water”, or שם מים “There is water”, or אש ומים “Fire and water”. He mingled fire with water and of them He made the heavens (Chagigah 12a).

ויקרא אלוקים לרקיע שמים, as I have already explained previously, the rakia is referred to as shamayim throughout the Torah, whereas the celestial regions in the spiritual sense are called shm’ey hashamyim, “the upper heavens.” Compare Nechemyah 9,6 where we are told:אתה עשית את השמים, שמי השמים וכל צבאם, “it is You Who have made the sky, the heavens and all their hosts.” In Deuteronomy 10,14 Moses wrote: והן לה' אלוקיך שמים ושמי השמים, “both the skies and the heavens are Yours, O Lord.”

ויקרא אלוקים לרקיע שמים. Seeing that activities occurring in the celestial regions reach us by means of G’d’s agents and not directly, the Torah had to tell us that G’d named the phenomenon, otherwise we would not have known this, [would have considered it as a result of an evolutionary process. Ed.] We know of this indirect activity of G’d when the Torah referred (verses 17-18) to “G’d placed them (the luminaries) in the רקיע השמים, and assigned to them the task to illuminate the earth, etc.”