Having taught us the Isur Melachah on Shabbos in the Aseres ha'Dibros (Sh'mos 20:10, why does the Torah repeat it here?
Rashi: To teach us that, even though Sh'mitah itself is called Shabbos, it does not override the weekly Shabbos, which applies throughout the year just like every other year. 1
Seforno: To prohibit (via an Asei) even acts that are not actually Melachos that are forbidden on Shabbos, but that entail exertion. 2
Having taught us the Isur of Mechamer (leading a laden animal on Shabbos. See Sh'mos 20:10), why does the Torah see fit to mention here "Lema'an Yanu'ach Shorcha va'Chamorcha"?
Rashi: It is an obligation to allow one's animals to 'rest', 1 by letting them eat the grass of the field, even though the owner is not permitted to detach whatever is attached to the ground.
Ramban: Taking "Lema'an" literally), it means performing all one's tasks during the six days of the week will enable the son of one's maidservant and the Ger to rest and testify on the Creation.
Seforno: The Torah is saying that, if one refrains from performing acts that entail work, but that are not actually Melachos (Refer to 23:12:1:2*), one's animals will also be able to enjoy a Shabbos rest. 2
Yerushalmi Shabbos, 5:3: To teach us Shevisas Beheimah
How about other animals, besides oxen and donkeys?
Rashi: The Pasuk extends to all animals. 1
Bearing in mind te Pasuk in Va'eschanan (5:14) "Lema'an Yanu'ach Avd'cha va'Amascha Kamocha" and "ve'Gercha asher bi'She'arecha", why does the Torah see fit to mention here "Ben Amasecha ve'ha'Ger"?
Rashi and Targum Yonasan: It is referring to an an uncircumcised son of a Shifchah 1 (and to a Ger Toshav
Aruch l'Ner (Yevamos 48b DH bi'Gemara): This is the opinion of R. Yishmael, who permits keeping Arel slaves; Aseres ha'Dibros discusses a Mahul (circumcised) slave. R. Akiva, who forbids keeping Arel slaves; must hold that Ben Amasecha is Mahul, and Aseres ha'Dibros discusses a bought slaves who did not circumcise yet. Moshav Zekenim - here we discuss a bought slave. (Aruch l'Ner - it is difficult to say that he is called Ben Amasecha because one bought him with his mother.)
Moshav Zekenim: He is commanded about Shabbos because it is equal to idolatry. Aseres ha'Dibros discusses a convert.
As opposed to our experience as slaves in Egypt, when we were forced to work seven days a week without respite - thereby rendering Shabbos a "Zeicher li'Yetzi'as Mitzrayim" (Seforno).