Why does the Torah repeat "Viyeshavtem la'Vetach Alehah"?
Rashi: To reinsure them that they will not need to be concerned about drought.
Ramban: It is an assurance that there will be enough to eat in Sh'mitah, and that they will not need to leave the land to seek food elsewhere.
Seforno: It is an assurance that there will be plenty to eat in the land, and that they will not have to suffer the embarrassment of having to go and purchase food from other nations.
Sifra: "la'Vetach", 'and not scattered and afraid'; "Alehah", 'and not in Galus'. 1
Oznayim la'Torah: The first time ? it is referring to the results of keeping the Chukim and Mishpatim, whereas here - where it follows a blessing of bountiful food, it is an assurance that nobiody will covet their land and they will safe and protected in it.
See Torah Temimah, note 108.
Having written "Venasnah ha'Aretz Piryah", why does the Torah add "Va'achaltem Lachm'chem la'Sova'?
Rashi and Targum Yonasan: To teach us that even in the stomach, the food will be blessed. 1
Seforno: To teach us that the fruit, in the sixth year will be highly sustaining - qualitatively, 2 in that the harvest of the sixth year will suffice for the seventh and eighth years as well.
Why did Rashi explain the end of the Pasuk before the beginning?
Mizrachi: In order to highlight the diference between "Viyeshavtem al ha'Aretz la'Vetach" and "Viyeshavtem al ha'Aretz la'Vetach in the previous Pasuk.