What is this Pasuk coming to teach us?
Rashi #1 and Ramban #1 (citing Kidushin 21a): It is coming to include houses and Avadim Ivrim in the obligation to release in the Yovel.
Rashi #2 and Rashbam: With reference to the following Parshah, 1 it is coming to obligate the purchaser to return the field, in the event that the owner comes to redeem it before the Yovel any time after two years.
Ramban and Seforno: It implies that the Dinim of Shemitah and Yovel apply throughout Eretz Yisrael, 2 but not in Chutz la'Aretz.
Ramban #2: It is a command to allow property throughout Eretz Yisrael to be redeemed by the owner. 3
See Ramban's objection to this explanation.
Ramban: To remove it from the hand of the person who currently has it - as on Yeshayah, 48:20 and in Shemos 6:6 - because Hashem wants to redeem the land from the one to whom He did not initially give it as an inheritance.
Ramban: Only in the land of our ancestral inheritance, including Eiver ha'Yarden and the other lands that we possessed - not just the Land of Hashem, in which the Beis-Hamikdash was built.