What do we learn from "v'Yashov he'Afar Al ha'Aretz keshe'Hayah"?
Rashi (from Eichah Rabah): [Am Yisrael] were initially in Bavel (Avraham and Sarah were there), and returned to Bavel.
Torah Temimah citing Shabbos 152b #1: In the future Tzadikim will be earth. "u'Rkav Atzamos Kin'ah" (Mishlei 14:30) - bones rot only if the person was jealous. If he was not, "v'El Afar Tashuv" will be fulfilled shortly before revival of the dead.
Torah Temimah citing Shabbos 152b #2: A Mes knows everything that is said in front of him until the Golel 1 is sealed 2 .
Rav Sadya Gaon: The body will come to its element - earth. Metzudas David - Adam was formed from earth, and returns to his initial state. Metzudas Tziyon - "Al ha'Aretz" is like El ha'Aretz.
Ibn Ezra: Only bones will remain in the body, and also they will return to be earth 3 .
Rashbam: Man, who is compared to earth, will return to be earth. Before this, he should repent!
Seforno: "He'Afar" is the earthly part [of man].
Rashi (Shabbos 152b): This is the coffin cover. Tosfos - it is a rock left on the coffin cover.
Shabbos 152b: Another opinion says, until the flesh is consumed. He learns from "Ach Besaro Alav Yich'av v'Nafsho Alav Te'eval" (Iyov 14:22).
After a very long time. (PF)
What do we learn from "veha'Ru'ach Tashuv El ha'Elokim Asher Nesanah"?
Rashi (from Eichah Rabah): This is Ru'ach ha'Kodesh. Once it departed, they were exiled.
Torah Temimah citing Shabbos 152b: Just like it was Tahor when it was given to you, return it Tahor!
Rav Sadya Gaon: The Nefesh returns to Hashem, who joined it to the body.
Ibn Ezra: This refutes those who say that the Ru'ach is temporary.
R. Avigdor: When the body is finished, the Neshamah does not return to it.
Seforno: It returns to Hashem to give an accounting of his deeds.
Metzudas David: The Ru'ach (Neshamah) returns to the place from which it was hewn. Hashem gave it at the time of birth.