מדרש אויף איוב 36:28

“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).

From where does the earth receive its [rain] water? Rabbi Eliezer says: From the water of the ocean,²⁹The ocean water evaporates to form clouds, and that water falls as rain. as it is written: “A mist would rise from the earth.” Rabbi Yehoshua said to him: But is the ocean water not salty?³⁰So how can you say that rain originates there? He said to him: It becomes sweetened in the clouds, as it is written: “Which the skies distill” (Job 36:28). Where is it distilled? In the skies. Rabbi Yehoshua says: [Rain comes] from the upper waters, as it is stated: “By the rains of the heavens it drinks water” (Deuteronomy 11:11). The clouds rise up from the earth to the firmament and there [from above] they receive it [rain] as from the mouth of a jug, as it is written: “Which cluster into rain from His mist” (Job 36:27). And they [the clouds] separate it [the water] like a type of sieve, so that no drop touches its counterpart, as it is written: “Dripping water, thick clouds of the skies [sheḥakim]” (II Samuel 22:12).
Why does he call it [the sky] sheḥakim? Rabbi Shimon ben Lakish said: It is because it crushes [shoḥakim] the water [into little pieces]. Rabbi Abba bar Kahana said: Like an omasum.³¹A digestive organ in ruminants that crushes their food. Rabbi Shmuel bar Naḥman said: Like an animal’s intestines.