Yalkut Shimoni on Torah 5:13

Rabbi Yehudah says: The world was created over six days, with each and every day's work, as it is written, "and it was so." But Rabbi Nechemyah says: From the first day the entire world was created, as it is said, "let the earth bring forth" (Genesis 1:24), a thing that had been prepared from the very beginning. A noble lady [matrona] asked Rabbi Yose ben Chalafta: In how many days did the Holy One, blessed be He, create His world? He said to her: From the first day. She said to him: From where do you know this? He said to her: Did you prepare a banquet? She said to him: Yes. He said to her: And how many kinds of dishes did you have? She said to him: Such and such. He said to him: And did you set them all before the guests at one time? She said to him: No; rather, I cooked all the dishes together, and I brought them in before the guests one by one. [So too God prepared all at the start and brought each forth in turn.] And all of this is from the verse, "for He is the Fashioner of all things" (Jeremiah 10:16).