When separating ma’aser and terumat ma’aser, one should take care to designate the proper amount: exactly one-tenth, neither more nor less. Produce that is normally measured by volume should be measured in that same manner; produce that is normally counted should be counted. When possible, it is best to calculate by weight, since weight is the most accurate method (MT, Laws of Terumot 3:11; Laws of Ma’aser 1:14).
When one is unable to weigh, measure, or count the produce, he may separate the tithes by estimate. If he intended to separate the correct amount, his separation is valid even if his estimate was significantly off, provided it was the kind of mistake people sometimes make. Still, the Sages cautioned: “Do not tithe excessively by estimation” (Avot 1:16). [6]
Today, the accepted practice is not to remove actual produce for the tithes themselves. Instead, one designates one-tenth of the produce in a specific location, such as the north or south side, and that portion becomes the ma’aser. This allows the amount designated as ma’aser to be exact. One then gives the value of the ma’aser to the levi or poor person, while ma’aser sheni is redeemed on a peruta.
The terumot, however, have sanctity and must be physically removed. After being removed, they are wrapped and placed respectfully in the trash. The amount removed must be more than one percent of the produce: one percent for terumat ma’aser, plus an additional amount for teruma gedola. If one removed only one percent or less, no amount remains for teruma gedola. Since his declaration assumes that teruma gedola is separated first, the entire separation is invalid, and he must separate terumot and ma’asrot again in the proper order. See Merkavat ha-Mishneh and Yeshu’ot Malko to MT, Laws of Ma’aser 13:19; Ma’adanei Eretz, Terumot 3:23:8.
Once terumot and ma’asrot have been designated, the designation has halakhic force, similar in this respect to vows and consecrations. Therefore, if one wants to be released from that designation – for example, because he realizes that the separation was made incorrectly – he may ask a Torah scholar, together with two others, to annul it under the rules of vow annulment. The produce then returns to the status of tevel (MT, Laws of Terumot 4:17). The same applies to ḥalla; see below, 10:13.[7]
[6]. Tosefta, Demai 8:10, and Yerushalmi, Demai 5:2, address one who designated the wrong amount as ma’aser: “One who separates less than the proper amount for his tithes – his tithes are in order, but his produce remains problematic. One who adds more than the proper amount for his tithes – his produce is in order, but his tithes remain problematic.”
If one deliberately designated less than one-tenth as ma’aser, some authorities maintain that the separation takes effect, but he must complete it by separating additional produce until he reaches the required tenth (Ribmatz; Rosh to Mishna, Terumot 4:1; Ramban; Ra’avad, Laws of Ma’aser 1:15; Vilna Gaon, YD 331:125). Others maintain that the separation is void since he did not designate a full tenth (MT, Laws of Terumot 3:7; Laws of Ma’aser 1:15; SA YD 331:77).
If one designated more than one-tenth as ma’aser rishon, the produce from which he separated may be eaten, since a full tenth was certainly removed. The separated portion itself, however, remains problematic. Only the required tenth has the status of ma’aser rishon; the extra produce added beyond that tenth remains tevel and still requires ma’aser sheni or ma’aser ani (Ramban and Ritva to Gittin 31a). Some maintain that once this extra produce has been mixed into the separated portion, there is no way to correct it (Meiri).
Some authorities are stringent and understand the earlier rule to apply even when one tried to separate the proper amount by estimation but ended up with too much or too little; see Mishpetei Eretz 18 note 18. This reading is difficult, both textually and logically. Many authorities state explicitly that the rule applies only when one intentionally increased or decreased the tithe. If, however, he intended to separate the proper amount and simply miscalculated, his separation is valid, even if he was estimating rather than measuring. This is the view of Rash (Terumot 1:7), Tosafot (Gittin 31a, s.v. nitelit), Kaftor Va-feraḥ ch. 24, Sha’arei Tzedek 10:11, and AHS 61:3. This also seems to follow from R. Yosi’s statement in Yerushalmi, Demai 5:2 that the court’s stipulation extended “to the point that the mind errs.” In other words, the Torah commands human beings to separate terumot and ma’asrot, and human beings cannot be perfectly precise. An ordinary human error therefore does not invalidate the tithes. Even the most precise scale cannot produce absolute precision, since the edible portion of each fruit varies depending on its peel, pit, or seeds, and no scale measures with perfect exactness. This is even more true when one separates by volume or by number, where ordinary variation will naturally lead some people to separate slightly more than one-tenth and others slightly less. Therefore, the mitzva cannot require absolute mathematical precision. A normal human miscalculation does not invalidate the separation. Still, the Sages instructed that, whenever possible, one should not separate by estimation. The goal is not absolute precision, which human beings cannot achieve, but to come as close as possible to the proper tenth.
[7]. One may seek annulment of the separation only while doing so will not create a new halakhic problem. Therefore, once people have already eaten from the produce, one should not annul the separation, as that would retroactively render what they ate tevel (Rema 323:1; Shakh YD 323:6). According to Ḥatam Sofer (YD 253), in pressing circumstances one may be lenient and seek annulment even after people have eaten from the produce. Since the produce was permitted when they ate it, the later annulment does not retroactively make them sinners. See Ha-Ma’aser Ve-ha-Teruma 4:27.
Once the owner has given the teruma to the kohen or the ma’aser to the levi, he can no longer seek annulment. Since the gift has already left his possession, the designation is no longer under his control (Rosh and Ran to Nedarim 59a; Mishpat Kohen 39:2; Ha-Ma’aser Ve-ha-Teruma 4:20).
If one separates again after the original separation was annulled, some maintain that no new berakha is recited. Since the original berakha may still cover the second separation, this is treated as a doubtful case of berakhot, and no new berakha is recited (Rashash to Nedarim 59a).
