Kesuvos 5a: The deeds of Tzadikim are greater than the creation of Shamayim and earth. One hand of Hashem made earth and one hand made Heaven, but the Mikdash is called the work of both hands - "Mikdash Hashem Konenu Yadecha" (Shemos 15:17).

Menachos 36b: Yemin is the right hand, and Yad (Stam) refers to the left.

Radak: Do not say that from the beginning of time, I am alone. Also before time, I was, for My hands formed Eretz and Shamayim, and time was created together with them. It says Yasdah, for the land is like a Yesod (foundation) for a building, for it is below, and Shamayim is stretched over it. It attributes Shamayim to the right hand, for it is more honored than Eretz. Also, the right hand's works last longer; particular beings in Shamayim last forever, but beings of the land do not. Tipechah means that He fixed it with His Tefach (hand) - "v'Shamayim ba'Zeres Tiken" (40:12).

Malbim: I made Shamayim va'Aretz at once, as if I set the foundation (Eretz) with My left hand, and at the same moment My right hand made the roof (Shamayim).

Radak, Chagigah 12a: This teaches that Shamayim and Eretz were created at once ¹ .

Radak citing his father: Hashem created Shamayim va'Aretz Yesh me'Ayin, from potential to actuality. He created them together; Shamayim ascended, as is normal for upper beings, and Eretz descended, like its nature. Had Hashem not stopped them, even now Shamayim would still be ascending and Eretz descending.

Radak citing Ibn Ezra: I made them, and when I call to them to fulfill My request, both of them stand in front of Me like servants.

Radak: I made them at the beginning of their creation, and all days of the world they stand together via My power. "Korei Ani Aleihem" - I influence My strength on them constantly, and via this they persist in their natures. It is as if I call to them to stand, and they stand.

Malbim: I call to Shamayim va'Aretz to ask the following question.