What is the significance of "uch'Mar'eh ka'Mar'eh"?
Rashi and Radak, citing Vayikra Rabah 1:14): There are nine appearances 1 written in this verse. Nevi'im saw via nine glasses, except for Moshe, who saw via one 2 . Therefore, his glass was clear; he truly saw. This is like a Piyut says 'visions polished with seven visions.' Radak ? nine alludes to the nine veils, and the 10th is Kodesh
Radak: Amidst the honor that illuminated, I saw like the vision when I came to destroy the city ? I saw the Merkavah. Also what I saw at the Kevar river, I saw now.
Malbim: I explained "u'Fnei ha'Kodesh ha'Mar'eh ka'Mar'eh" (41:21) - Pnei ha'Kodesh seemed to him like a Mar'eh (mirror) in which one sees what is opposite it. He saw like the vision of the Merkavah 3 . The Mikdash that Yechezkel saw built in Har Hashem. This is the image and glass in which he saw these two great forms, of the great and small worlds, and Shechinas Hashem which is clothed in the world and in the Nefesh. Like one who looks in a mirror sees his own image, so [Yechezkel] looked in the 'mirror' of the Mikdash [at] the form of the Merkavah that dwells in the great world, and Merkavas Hashem that dwells in the Nefesh that he saw in the vision, and about the Merkavah that he saw in Pnei ha'Kodesh it says "uch'Mar'eh ka'Mar'eh Asher Ra'isi." I.e. I saw now in Bayis Shelishi, which is the third Merkavah that he saw. He saw that Elokus will be revealed with an exalted power and great authority. What he saw when coming to destroy the city hints to the Churban. He saw also other visions hinting to dislocation and Galus of the Shechinah with Yisrael ? the final Galus.
I.e. including the three times that it says "Ra'isi". "U'Mar'os" counts as two. (PF)
Radak: "U'Mar'eh v'Lo v'Chidos" (Bamidbar 12:8. We fixed the text based on the Midrash. What was written "ba'Mar'eh Elav Esvada" is a printing mistake. That verse discusses other Nevi'im! - PF)
Malbim: The revelation of Hashem's Merkavah in the small Mikdash resembles the revelation of Hashem's Merkavah in the great Mikdash ? the world, which He created in the image of His honor. Similarly, Merkavas Hashem in the great world resembles Merkavas Hashem that dwells in the small world, i.e. man, who was made in Hashem's Tzelem. The Yichus (relation) between Elokus that dwells in man, in the Mikdash of the heart, Ru'ach and Nefesh, in the garment of the body, is itself the Yichus in which Elokus dwells in the great Mikdash, i.e. the great man, which is the Klal of the existence that Hashem made for His honor.
When did he come to destroy the city?
Rashi: This was "v'Hisvisa Tav"; "Karvu Pekudos ha'Ir" (9:4, 1).
Radak: Yechezkel did not come to destroy it! He came when six men came to destroy it.
Radak citing Targum Yonasan: When I prophesized to destroy the city.
Why does it say "El Nehar Kevar"?
Radak: "El" is like Al. There are many verses like this.
What is the significance of the three times it says "Ra'isi"?
Malbim ? Yechezkel saw the Merkavah in three conducts. (a) When they came to destroy the city ? it left with anger, to destroy. (b) The first time, at the Kevar river ? it left its place to go with the exiles to the four directions of Shamayim. This is amidst His mercy, lest they be finished in their Galus. Even so, during the entire Galus He will conduct via officers above ? the Shechinah is clothed in the officer under which Yisrael are placed. (c) The Merkavah that he saw when He showed to him the future Mikdash ? Hashem's conduct when He will return His Shechinah to Tziyon. It will be wondrously miraculous. When he returned to the eastern gate, he saw the Merkavah in these three changing visions. He informed him that after Bayis Sheni will be built, He will return to destroy it due to the sins of Yisrael. This is why he saw when they came to destroy the city. Then He showed to him that afterwards Yisrael will be exiled again and scattered to the four directions, and Hashem went out with them in His Merkavah to the Golah to guard them. Therefore, he saw the Merkavah by Nehar Kevar. Then He showed that He will return to Bayis Shelishi and dwell there forever 1 `.
Malbim: In the first vision he understood conduct via Chayos and the world of the angels. In the second vision he understood the conduct that will be, via Serafim and Olam ha'Kisei. In the third vision for the future, he understood conduct via Elokus in Olam ha'Atzeilus.
Why did he fall on his face?
Malbim: He understood that after Bayis Sheni will be built, it will be destroyed and Yisrael will be exiled again.