מדרש אויף איוב 36:27

We are taught in a Baraitha: R. Eliezer said: "The entire world drinks of the water of the ocean [coming from below]; as it is said (Gen. 2, 6) But there went up a mist from the earth and watered the whole face of the ground." "How can that be?" R. Joshua said to him. "Are not the waters of the ocean salty?" Whereupon he replied: "They become sweet in the clouds." R. Joshua, however, says: "The entire world drinks of the water that comes from above, as it is said (Deut. 11, 11) From the rain of heaven doth it drink water. But how is the passage: T' at there went up a mist from the earth, to be taken? It means that clouds rise towards heaven, where they open their mouths like bags and drink in the water; as it is said (Job 36, 27) For he taketh away drops of water, which are purified into rain in the mist; and the mist is porous like a sieve, through which the rain descends to the earth; as it is said (II Sam. 22, 12) Heavy masses of water, thick clouds of the skies, and the space from one drop to another is only the width of a hair. From this it may be inferred that the day of rain is as great as was the day of creation of heaven and earth; as it is said (Job 9, 10) Who doth great things which are quite unsearchable; and it is also written (Ib. 5, 10) Who giveth rain upon the surface of the earth; and it is also written (Is. 40, 28) Dost thou not know? Hast thou not heard? The God of everlasting is the Lord, etc., unsearchable is his understanding; and again it is written (Ps. 65, 7) Who setteth firmly the mountains, etc.

The firmament is similar to a pool of water and above the pool is a dome. Because of the pool there is condensation of thick drops, and they descend into the salt water but do not intermingle. Rabbi Yona said: Do not wonder; the Jordan passes through the Sea of Tiberias but does not intermingle [with its water].
There is miraculous process involved in this matter.¹²The matter of rainfall. When a person sifts wheat or stubble in a sieve, before they fall two or three fingerbreadths they are already intermingled, but these [raindrops] travel a distance of several years and do not intermingle with one another.
Rabbi Yudan ben Rabbi Shimon says: He rains them down by measure, as it is stated: “For He deducts [yigara] drops of water” (Job 36:27), just as it says: “It will be deducted [venigra] from your valuation” (Leviticus 27:18).¹³All deduction is by measure.
The thickness of the earth is equivalent to the thickness of the firmament, as it is stated: “It is He who sits over the circuit [ḥug] of the earth…” (Isaiah 40:22), “in the circuit [ḥug] of the heavens He makes His way” (Job 22:14) – the words ḥug ḥug provide a verbal analogy.¹⁴Establishing a comparison between the earth and the heavens. Rav Aḥa said in the name of Rabbi Ḥanina: It is like a sheet of metal.¹⁵The firmament is not as thick as the earth; rather it is extremely thin. Rabbi Yehoshua bar Rabbi Neḥemya said: It is approximately two or three fingerbreadths [thick].
Rabbi Shimon ben Pazi said: The upper waters contain approximately thirty kesustas¹⁶A certain measure of volume. more than the lower – “and let it divide between water and water [lamayim]” – lamed equals thirty.¹⁷The numerical value of lamayim is thirty more than the numerical value of mayim. The Rabbis say: It is half and half.

“All the rivers go to the sea, yet the sea is not full; to the place that the rivers go, they go there again” (Ecclesiastes 1:7).
“All the rivers go to the sea,” and from where does the earth drink?³²Which waters are provided to the earth in the form of rain? Rabbi Eliezer and Rabbi Yehoshua, Rabbi Eliezer says: It drinks from the water of the ocean, as it is stated: “A mist went up from the earth [and watered the entire face of the ground]” (Genesis 2:6).³³Thus, it is water from the earth that turns to vapor and then falls as rain. Rabbi Yehoshua said to him: ‘Isn’t the water of the ocean salty?’ He said to him: ‘They are sweetened in the clouds, as it is written: “Which the skies pour down” (Job 36:28). Where do they become what pours down? It is in the skies.’ Rabbi Yehoshua says: [The earth] drinks from the upper waters, as it is stated: “From the rain of the heavens you drink water” (Deuteronomy 11:11). The clouds ascend from the earth to the heavens and receive [the water] as though from the mouth of a bottle, as it is written: “Which distill rain to His mist” (Job 36:27). They separate them like a sieve and one drop does not touch another, as it is written: “The amassing of water, thick clouds of the skies’ (II Samuel 22:12). Why does it call them skies [sheḥakim]? It is because they crush [shoḥekin] the water.³⁴Separating the water into separate drops. Rabbi Abba bar Kahana said: Like an omasum.³⁵The third stomach in the animal that grinds the food. Rabbi Shmuel bar Naḥman said: Like the intestines of an animal.³⁶That crush the food. It is as Rabbi Yehoshua said: A day of rainfall is great, as it is equivalent to the entire act of Creation.³⁷Rabbi Yehoshua’s opinion that rainwater is from the upper waters in the heavens, which comes to earth, is consistent with his statement that this process is an act equivalent to Creation itself (Midrash HaMevoar). What is the reason? “Who performs great things beyond scrutiny and wonders beyond number” (Job 9:10); with what? “Who gives water on the face of the earth…” (Job 5:10).