Which Chukim and Mishpatim is the Torah referring to?
Ramban and Seforno: "Chukim" refers to the Chukim of Shemitah and Yovel, and "Mishpatim", to the laws of buying and selling that are connected with Yovel.
Why does the Torah insert the phrase "vi'Yeshavtem al ha'Aretz la'Vetach" here?
Rashi. Ramban and Seforno: Because it is on account of the sin of Shemitah
that Yisrael are exiled from the land.
Rashi and Seforno:
As the Torah specifically writes in Bechukosai, 26:34 & 26:43. Rashi:
Indeed, the seventy years of Galus Bavel were a punishment for the seventy Shemitah- years that they contravened.