Ramban #1 and Moshav Zekenim #1: It is the way the Torah normally speaks. ¹

Ramban #2 and Moshav Zekenim #2 (citing the Yerushalmi in Kil'ayim): To teach us that someone who works his land in the Sh'mitah transgresses an Asei ² (as well as the La'av in the following Pasuk.

Ramban #3 (citing the Mechilta in Mishpatim) and Seforno: To teach us that, when Yisrael do the will of Hashem they will experience one Sh'mitah (per seven years), as the Torah writes "Sheish Shanim Tizra es Artzecha ... "; but if they don't, they will have to keep four Sh'mitos - by leaving the land fallow in the first, third and fifth years, ³ followed by the Sh'mitah in the seventh.

Moshav Zekenim: It is written after "Shabbos la'Hashem" to teach us that if we observe Sh'mitah properly, we will sow our fields; if not, we will have to sell them (and subsequently, also our houses and our daughters - Kidushin 20a).

Oznayim la'Torah: To highlight the miracle that, when one keeps the Sh'mitah, one will be able to to till the land for six consecutive years ? as opposed to the normal system, where the land is left fallow every second year. ⁴

Yerushalmi Kil'ayim, 5:1: Bearing in mind the "Veshavsah ha'Aretz Shabbos la'Hashem" - in Pasuk #2, it teaches us ('Im Eino Inyan') that all other Melachos - besides planting and pruning, are only subject to an Asei and are not therefore sibject to Malkos. ⁵

Oznayim la'Torah: To teach us that the time that one is prohibited from plowing a cornfield (until Pesach) differs from the time that one may not plow a foeld of trees (until Shavu'os). ¹

Rashbam: It means that, during the first six years of the Sh'mitah cycle, one is permitted to gather the produce of one's own field. ¹

Yerushalmi Ma'asros, 5:2: Based on its juxtaposition to "u'va'Shanah ha'Shevi'is", it permits harvesting produce in the Sh'mitah that attained one third of its growth in the sixth year. ²