The first two perakim of masekhet Shvi'it outline the various laws pertaining to the period prior to shemitta known as tosefet shvi'it. Though most of the halakhot of shemitta are launched on Rosh Hashana of the shemitta year, there are some halakhot that apply in the months preceding the year. This shiur will address the structure and nature of this preliminary period.
The gemara in Mo'ed Katan (3b-4a) establishes a machloket between Rebbi Akiva and Rebbi Yishmael regarding the source for the tosefet shvi'it. Both agree that certain forbidden actions (plowing, possibly planting) are forbidden thirty days before Rosh Hashana. What they argue about is the source of this prohibition.
Rebbi Akiva derives this period from a pasuk in parashat Mishpatim which, though it describes the laws of Shabbat, is taken as a reference to tosefet shvi'it. The pasuk writes (Shemot 34:21), "You should work for six days and on the seventh you should rest - refrain from plowing and reaping." Rebbi Akiva recognizes the final clause as superfluous since we already know that it is forbidden to plow and reap on Shabbat (since these activities are included in the set of 39 activities vital to the routine of the Mikdash). Hence, it must refer to a different type of shabbat - namely the shabbat that shemitta entails (resting from working the land). However, we already know that one cannot reap on shvi'it, from Vayikra 25:4-5 (we also presumably know that one cannot plow, although the pasuk does not specifically ban this). Hence, this extra clause forbidding plowing and reaping must refer to the 'brackets' of shemitta. One cannot plow for thirty days leading up to the shemitta year, and similarly one cannot harvest - during the eighth year - the fruits that grew during the seventh year of shemitta. Rebbi Akiva takes this phrase as a source for tosefet shvi'it both before the actual year (not plowing thirty days before) as well as afterwards (not harvesting the shemitta fruits).
Rebbi Yishmael for his part claims that the pre-shemitta prohibitions have no explicit source in the Torah but were transmitted as a halakha le-Moshe mi-Sinai. Several gemarot (see Mo'ed Katan, Sukka 34a) discuss the halakha le-Moshe mi-Sinai that allows someone to plow 'eser netiot,' a tract of land that contains ten new seedlings, right until the shemitta year actually begins on Rosh Hashana. We may infer from this special dispensation afforded weak and fledgling seedlings that other lands cannot be plowed during this thirty-day period. According to Rebbi Yishmael, the same halakha le-Moshe mi-Sinai prohibits plowing regular lands during the thirty days prior to shemitta but permits the plowing of eser netiot until Rosh Hashana itself.
The gemara concludes that according to Rebbi Yishmael, the Biblical laws pertaining to tosefet shvi'it were canceled after the Beit Ha-mikdash was destroyed. The halakha le-Moshe mi-Sinai itself directed that the tosefet shvi'it period is only mandatory when the Beit Ha-mikdash was standing. The Rambam appears to rule according to Rebbi Yishmael, that a halakha le-Moshe mi-Sinai serves as the source of the tosefet shvi'it period and that without a Beit Ha-mikdash this period is suspended.
How are we to understand the nature of this prohibition? A very revealing perspective emerges from an important position adopted by Rabbenu Tam. Although the tosefet shemitta period begins thirty days before shemitta, the Chakhamim extended certain issurim for longer periods. The first mishna in the second perek of Shvi'it comments that all plowing is to cease after Pesach prior to shvi'it, while the first mishna of the first perek allows plowing of orchards until Shavuot. After Shavuot, however, all plowing must be terminated (except for the special exception granted eser netiot - a field containing seedlings). In light of these prohibitions, a gemara in Rosh Hashana seems somewhat troubling. The gemara in Rosh Hashana (9b) prohibits someone from planting a tree within the thirty day period preceding shemitta. Rabbenu Tam is troubled by the discrepancy between the prohibition to plow, which the Chakhamim extended to Shavuot or Pesach, and the issur to plant, which only applies during the thirty day period prior to shemitta. Why didn't the Chakhamim broaden the issur to plant as they did the issur to plow?
To explain this disparity, Rabbenu Tam suggests a landmark opinion. Classically we might view tosefet shvi'it as some legal extension of shemitta. Either the pasuk or the halakha le-Moshe mi-Sinai orders us to begin the experience of shemitta earlier than Rosh Hashana, much in the same manner that we begin Shabbat and Yom Kippur early. Rabbenu Tam disputes this notion. Plowing is forbidden during the months prior to the shemitta year because it will improve the land during shemitta. Since the effects of this plowing will be felt during shemitta, plowing must be ceased prior to the commencement of the actual shemitta year. This principle doesn't apply in the case of planting trees, since this work in no way prepares the field or improves it for work during shemitta. Hence, Rabbenu Tam argues, mi-deoraita, only plowing is forbidden during tosefet shemitta. The issur to plant thirty days before shemitta is only Rabbinical in nature. Therefore, the Rabanan extended the Biblical issur to plow thirty days before to include all plowing from Pesach onwards. They did not, however, extend the issur to plant, as the original prohibition is only Rabbinical in nature. Rabbenu Tam asserts that tosefet shvi'it is not to be understood as an extension of shemitta, but rather a prohibition of certain labors whose effects will be felt during shemitta proper.
A similar sense arises from the Rambam, who, in his introduction to the third perek of Hilkhot Shemitta ve-Yovel, argues that work during tosefet shvi'it is forbidden since such work "improves (metakna) the land for shvi'it." Though he doesn't distinguish between plowing and planting (he employs a generic term "avodat ha-aretz") it appears as if planting during this period is only forbidden mi-derabanan. In halakha 11 he writes that planting thirty days before is forbidden because of mar'it ayin; people who view newly planted trees during shemitta will suspect that they were actually planted during shemitta. The Rambam - both in his syntax and in his explanation of why planting within thirty days is forbidden - appears to agree with Rabbenu Tam: tosefet shvi'it is not an extension of shemitta, but rather a period during which the preparatory work of plowing is forbidden.
Interestingly enough, one might have claimed that the differing views of tosefet shvi'it depend upon the source of this law. Rebbi Yishmael's source - nondescript as it is - cannot accurately reveal the nature of the halakha. Yet Rebbi Akiva's source would seem to strongly evoke Rabbenu Tam's view. By writing "be-charish u-vakatzir tishbot," the Torah forbids the plowing of the sixth year - seemingly emphasizing plowing and not other forms of work. In addition, the Yerushalmi (Shvi'it 1:1) adds an interesting phrase to Rebbi Akiva's derasha – "charish she-kitzuro ba-shevi'i" - refrain from plowing land whose produce would normally be harvested during the shemitta year. This phraseology underscores the logic posed by Rabbenu Tam - since this plowing facilitates planting and harvesting of the shemitta year, it must be ceased prior to the inception of the year itself. Not only are we forbidden from actively working the land, we may not bring it to a state of readiness for normal agricultural activity.
A similar tone is sounded by Rabbenu Tam in a Tosafot in Rosh Hashana (9a). Having secured a pasuk for Rebbi Akiva's tosefet shvi'it, the gemara wonders how Rebbi Yishmael will derive the laws of tosefet Shabbat or Yom Kippur. Even if he has a halakha le-Moshe mi-Sinai regarding shvi'it, how will he derive tosefet Shabbat and tosefet Yom Kippur? Tosafot ask why the gemara does not suggest that Shabbat and Yom Kippur be derived from shvi'it? To this Rabbenu Tam answers that Rebbi Yishmael's halakha le-Moshe mi-Sinai source only establishes a prohibition for the period PRIOR to shemitta. In as much as we are seeking to establish tosefet Shabbat/Yom Kippur both before and after, we must locate an alternate source. This delimitation is also consistent with Rabbenu Tam's approach. If we view tosefet shvi'it as some form of extension, we would presumably extend shemitta both before and after the actual seventh year. If, however, we do not extend shemitta but proscribe certain labors whose potential benefits will be enjoyed during shemitta, we can easily understand limiting this phenomenon to the period prior to shemitta but not after shemitta. Rabbenu Tam claims that tosefet shvi'it - at least according to Rebbi Yishmael - would only apply to the periods preceding shemitta, a statement that echoes his view pertaining to tosefet shemitta in general.
There is one glaring difficulty with Rabbenu Tam's approach. That same gemara that - for whatever reason - sought a source for tosefet Shabbat/Yom Kippur according to Rebbi Yishmael was secure in not looking for a pasuk according to Rebbi Akiva. Since Rebbi Akiva derives tosefet shvi'it from a pasuk ("be-charish u-vakatzir tishbot"), he can utilize this pasuk as the source for tosefet in general. Many Rishonim and Acharonim are concerned with Rebbi Akiva's ability to derive tosefet Shabbat from tosefet shvi'it (see Rebbi Akiva Eiger's comments as well as the Turei Even). Many Rishonim (Ba'al Ha-Maor) reinterpret this gemara and claim that Rebbi Akiva would not derive tosefet Shabbat from shvi'it, but the chakhmei Sefarad (Ritva and Rashba) maintain the simple reading of the gemara. If indeed Rabbenu Tam is correct that tosefet shvi'it does not entail an extension of shemitta but rather the prohibition of preliminary work to benefit shemitta itself, it would be impossible to compare tosefet shvi'it to tosefet Shabbat or tosefet Yom Kippur. By the gemara's willingness to allow that comparison according to Rebbi Akiva, it would appear that at least he viewed tosefet shvi'it as a halakhic extension of the year. This model - of halakhic extensions - can then be extrapolated to Shabbat and Yom Kippur.