The 134th mitzvah is that we are commanded to disown everything which the land produces during the shemittah year; to release everything which grows on our property for the use of any living creature.

The source of this commandment is G‑d's statement,1 "During the seventh year, you must let it be public and withdraw from it."

The Mechilta [D'Rashbi] says: "Grapes and olives were already included [in the general command]. Why were they singled out? To make a comparison — just as grapes, which are covered by the positive commandment, also have a prohibition, so too everything covered by the positive commandment also has a prohibition."

I will explain the meaning of this statement. The verse, "During the seventh year, you must let it be public and withdraw from it" includes the release of everything which grows during shemittah: grapes, figs, peaches, pomegranates, wheat, barley, etc. Therefore the release of all produce is a positive commandment. Afterwards, the verse continues, "This also applies to your vineyard and your olive grove." But they were already included in this commandment, which covered everything which grows from the ground! [Our Sages therefore explain that] grapes and olives are mentioned separately because there is a special verse2 which explicitly creates a prohibition on grapes: "Do not gather the grapes on your unpruned vines." [The comparison therefore teaches us that] just as releasing grapes is a positive commandment, and holding them is a prohibition, so too anything which grows during shemittah — which, as explained above, there is a positive commandment to release — there is a prohibition to hold. Therefore the law regarding olives is identical to that regarding grapes — there is a positive commandment and a prohibition; and other types of produce have the same law as olives.

From the above discussion it is clear that the release of produce which grows during shemittah counts as a positive commandment.

The details of this mitzvah are explained in tractate Sh'vi'is. It is a Biblical commandment only for produce of Eretz Yisrael.3