When separating terumot and ma’asrot, the portion set aside must have the same halakhic status as the produce it is meant to permit. Produce that is exempt cannot be used for produce subject to the obligation, and produce subject to the obligation cannot be used for exempt produce. Therefore, one may not separate from produce grown outside Eretz Yisrael, or from produce from which terumot and ma’asrot have already been separated, for produce still subject to the obligation. The reverse is also true. If one did so, the separation has no effect, and he must separate again from the produce subject to the obligation (MT, Laws of Terumot 5:12).
The same concern applies when the status of the produce is uncertain. If there are two batches of produce from different places, and each may or may not have been tithed, one should not separate from one batch for the other. One batch may already be tithed while the obligation still applies to the other. If so, he would be separating from exempt produce for produce still subject to the obligation, or the reverse.
The same principle applies across different levels of obligation. One may not separate from produce obligated only by rabbinic law for produce obligated by Torah law. Nor may one separate from produce obligated by Torah law for produce obligated only by rabbinic law.
The obligation applies by Torah law when the field owner grew the produce for his household, or when someone bought it from the field owner before its processing was complete and then completed the processing himself for his household. The obligation applies by rabbinic law when the field owner grew the produce for sale. The same is true of produce grown in an unperforated pot; the obligation applies only by rabbinic law. The law of one who mistakenly separated from one level of obligation for the other is explained in the note. [2]
There can even be different levels within rabbinic obligation itself. Some produce is subject to one rabbinic enactment, while other produce is subject to two rabbinic enactments. Ideally, one should not separate from one category for the other. Therefore, even though today all terumot and ma’asrot obligations are rabbinic (see below, 12:11), one should not separate from grapes harvested for home use for grapes harvested for sale. Nevertheless, if one did separate from one for the other, he has fulfilled his obligation. [3]
[2]. When one separates from produce obligated by Torah law for produce obligated only by rabbinic law, the separation is effective for the second batch, and that produce may now be eaten. However, a problem remains with the produce he designated as terumot and ma’asrot. Since the second batch is subject only to a rabbinic obligation, it is considered exempt by Torah law. From the Torah’s perspective, then, he separated from obligated produce for exempt produce, which has no effect. As a result, the produce he designated still has the status of tevel and requires its own separation.
The question is how to correct the status of that designated produce. According to Rambam, one must separate terumot and ma’asrot for it from other produce (MT, Laws of Terumot 5:16). Ri explains that one should not correct it by separating from the designated produce itself, because he might mistakenly eat the remainder, even though he had previously treated that produce as terumot and ma’asrot (Tosafot, Yevamot 89b, s.v. mi-makom). According to Rashi in Kiddushin 46b and Meiri, however, one may separate from it for itself, because there is no such concern.
The reverse case has a different consequence. If one separated from produce obligated only by rabbinic law for produce obligated by Torah law, the separation takes effect only on the rabbinic level. Since, from the Torah’s perspective, he separated from exempt produce for obligated produce, the Torah obligation remains in place. He must therefore separate terumot and ma’asrot again from the produce obligated by Torah law (MT, Laws of Terumot 5:14).
[3]. According to Turei Even (Megilla 19b), one may even initially separate from produce with one layer of rabbinic obligation for produce with two layers, and the reverse. Most authorities, however, maintain that one should not do so initially. This is the position of Maharam of Rothenburg (§423), cited in Beit Yosef YD 330:6, as well as Mishneh la-Melekh, Sha’arei Tzedek, Ha-Ma’aser Ve-ha-Teruma, and Kerem Tziyon. Nevertheless, if one already separated from one for the other, he has fulfilled his obligation, since both categories are ultimately subject to a rabbinic obligation (Torat Ha-aretz; Ḥallat Leḥem; Mishpetei Eretz 8, note 30; see below, 12, note 21).
Ideally, one should also avoid separating from produce with two layers of rabbinic obligation for produce with three. In pressing circumstances, however, one may be lenient. These situations are common today. The Aḥaronim agree that nowadays terumot and ma’asrot are rabbinic, and most authorities maintain that, even in principle, most fruits are obligated only rabbinically, except for grain, wine, and oil. Therefore, when some produce is intended for household use and some for sale, the case generally involves produce with two layers of rabbinic obligation and produce with three (R. Azriel Ariel, “Separating Terumot and Ma’asrot in the Public System,” p. 53).
