Just as the vastness of the sea dwarfs us and makes us mindful of death, so too, according to Calvin, should the falling of rain, for God’s providential ordering of its limits is no different from his ordering the limits of the seas.
One of the quirkier parts of the early books of Genesis for modern readers is the way in which it speaks of “waters above” and “waters below.” We first get this on the second day, when God creates the sky:
And God said, “Let there be an expanse in the midst of the waters, and let it separate the waters from the waters.” And God made the expanse and separated the waters that were under the expanse from the waters that were above the expanse. And it was so. And God called the expanse Heaven. And there was evening and there was morning, the second day.
The idea seems to recur in Gen. 2:5-7:
When no bush of the field was yet in the land and no small plant of the field had yet sprung up—for the Lord God had not caused it to rain on the land, and there was no man to work the ground, and a mist was going up from the land and was watering the whole face of the ground— then the Lord God formed the man of dust from the ground and breathed into his nostrils the breath of life, and the man became a living creature.
Then, when the flood arrives in Gen. 7:11-12, we find waters above and below once more:
In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened. And rain fell upon the earth for forty days and forty nights.
The idea seems inherently odd to us, given our modern understanding of the water cycle. We see all water on earth as being in constant motion, evaporating upwards before forming into clouds and coming down again as precipitation. We no longer picture a static “storehouse” (cf. Job 38:22) of water above us, distinctly separated from the water in the seas, lakes, and rivers down here. Because of our understanding of gravity, we see the primary “resting place” of water as down here on the ground, since it will always go with gravitational pull in its solid or liquid forms.
This further contrasts with a prevailing medieval/ancient Christian view of creation, which regarded God as directly holding the limits of water in place, a la Job 38:8-11. This view rested on a few medieval/ancient physical and cosmological assumptions: they viewed the cosmos as being structured as a series of concentric, Russian Doll-like spheres, and these spheres included the four elements (Earth, Water, Air, and Fire). Earth sat at the bottom, clearly being the heaviest element. But if water is lighter than earth, why then is the earth not entirely covered with water, which should naturally rise above it? The broad Christian answer was the miraculous providence of God, who held the waters back to allow for human life. I’ve described this as an ancient/medieval view, but it remained in place in the early modern era, and was that of Reformers like John Calvin.