The heavenly ocean and the earthly ocean
Genesis 1:6 reads ‘And God said, ‘Let there be a firmament in the midst of the waters (mayim), and let it divide the waters from the waters.’
It is difficult for us to think like an ancient human. We are taught the water cycle at an early age. We give our children books entitled ‘Why is the sky blue?’ But the Hebrews did not have access to the same knowledge we have today. When they looked at the sky, they saw, just beyond the horizon, a vast blue, so far away that even the sun seemed to be contained by it. At night they saw lights twinkling in the sky against a deep black. There is only one thing on earth that is vast and blue: the ocean. And where does rain come from? The sky. It only made sense that this blue sky was in fact a heavenly ocean.
