מדרש אויף שמות 19:20

SUCCAH (Fol. 5) We have been taught in a Baraitha: R. Jose says: "Never did the Shechina come down below [on earth], and Moses and Elijah never ascended to heaven; for it is written (Ps. 115, 16) The heavens are the heavens of the Lord, but the earth hath He given to the children of man." Then, the Shechina, you contend, never came down below? Behold, it is written (Ex. 19, 20) And the Lord came down upon Mount Sinai. This was ten spans above the ground. But it is written (Zech. 14, 4) And his feet will stand on that day upon the mount of Zeithim (Olives). This was ten spans above the ground. Again, [let me ask], is it indeed a fact that neither Moses nor Elijah ever ascended to heaven? Behold, it is written (Ex. 19, 3) And Moses went up unto God? This means below ten spans. But it is written (II Kings 2, 11) And Elijah went up by a storm wind into heaven. This also means below ten spans. But it is written (Job 26, 9) He lays hold of the face of His throne and spreads His cloud over him; and R. Tanchtum said: "This means to teach us that the Almighty spread the brightness of the Shechina and enveloped Moses with encouragement." This also refers to below these ten spans. However, it is written, he (Moses) lays hold of the face of His throne [hence they were both together]. He brought down His throne close to ten spans, where Moses took hold of it.

Alternatively, "These days were formed, but not one from them" [Psalms 139:16] is refering to Yom Kippur for (the nation of) Israel. {continuing}

"Who has ascended to Heaven and come down? Who has gathered the wind in the hollows of his hands? Who has bound water in a mantle?^*Poetic expression for the manner in which rain is enclosed within a cloud (Jastrow); see Job 26:8 (see below) Who established all the extremities of the Earth? What is his name and what is his son's name, if you know?" (Prov. 30:4.) "Who has ascended to Heaven" -- that is the Holy One Blessed be He, as is written in that regard: "God ascended with sounds of exultation (teruah)" (Ps. 47:6). "And come down" -- "And the Lord descended upon Mount Sinai" (Ex. 19:20). "Who gathered wind" -- "He who has the soul of every living being in His hand, etc." (Job 12:10). "Who bound water"-- "He binds water in His clouds" (Job 26:8). "Who established all the extremities of the Earth?" -- "The Lord causes death and brings to life" (1 Sam. 2:6). "And what is his name?" -- Rock is His name, Shaddai is his name, the Lord of Hosts is His name. "And what is the name of His son?" -- "My son, my first born, is Israel" (Ex. 4:22) is His [son's] name.
Another interpretation: "Who has ascended to Heaven?" Who is the one whose prayer ascends to Heaven and causes the rains to fall? He who separates his tithes with the hollows of his hands -- it is he who brings down dew and rainfall eternally. "Who has gathered the wind in the hollows of his hands? Who has bound water in a mantle? Who established all the extremities of the Earth?" Who is the one whose prayer does not ascend to Heaven and does not cause the rains to fall? He who does not separate his tithes with the hollows of his hands -- it is he who stops the Heavens from bringing down dew and rainfall eternally.
Another interpretation: "Who has ascended to Heaven?" -- that is Elijah, about whom it is written, "And Elijah ascended in a whirlwind to Heaven" (2 Kings 2:11). "And come down" -- "[The angel of Hashem said to Elijah,] 'Go down with him, do not be afraid,'" (2 Kings 1:15). Who has gathered the wind in the hollows of his hands?" -- "[Ejijah the Tishbite from the settlers of Gilead, said to Ahab, 'As lives] Hashem, the God of Israel, who I have stood before, [there will be no dew or rain in these years except at my word]'" (1 Kings 17:1). "Who bound up water [in a garment]?" -- "And Elijah took his mantle and rolled it up, [and he struck the waters]" (2 Kings 2:8). "Who established all the extremities of the Earth?" -- "And Elijah said, 'See, your son lives!'" (1 Kings 17:23).^*Commentators note that the Hebrew phrase מי הקים כל אפסי ארץ ("Who established all the extremities of the Earth"), can also be rendered "Who has raised up (hekim) all the nothingness (afsei) of the Earth"; i.e., Elijah raised from death (nothingness) the child of the widow from Tzarphatah.
Another interpretation: "Who has ascended to Heaven?" -- that is Moses, about whom it is written, "And Moses ascended to God" (Ex. 19:3). "And come down" -- "And Moses come down from the mountain" (Ex. 19:14). "Who has gathered the wind?" -- "As soon as I have gone out of the city, [I will spread my hands to Hashem, [and] the thunder will cease and the lightning will be no more]" (Ex. 9:29). "Who has bound water?" -- "The waters stood up in a heap" (Ex. 15:9). "Who has established (hekim) all the extremities of the Earth?" -- that is the Tent of Meeting, as it is said, "And it was on the day that Moses completed [establishing (l'kayem) the Tabernacle]." For the world was established with it.
Rabbi Yehoshua ben Levi, in the name of Rabbi Shimon ben Yochai: "Establishing a tabernacle" is not stated; rather, "Establishing the Tabernacle." Before it was established, the world was wobbling; once the Tabernacle was established, the world had a solid base. Therefore it is said, "And it was on the day that Moses completed, etc."