Arcana Coelestia #1037
1037. That 'and God said' means that it was so has been stated and shown already; for God's or Jehovah's saying, or His having said, means that it was so. Because the most ancient people used to weave together as a historical tale things to do with the Church, they would say, when wishing to assert that something was so, 'God said' or 'Jehovah said'. With them this was a commonplace expression for asserting and confirming something.
Jeremiah 31:31-33
31
Behold, the days come, says Yahweh, that I will make a new covenant with the house of Israel, and with the house of Judah:
32
not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they broke, although I was a husband to them, says Yahweh.
33
But this is the covenant that I will make with the house of Israel after those days, says Yahweh: I will put my law in their inward parts, and in their heart will I write it; and I will be their God, and they shall be my people:
