Halacha

הלכה א
כָּל אֹכֶל אָדָם הַנִּשְׁמָר שֶׁגִּדּוּלָיו מִן הָאָרֶץ חַיָּב בִּתְרוּמָה. וּמִצְוַת עֲשֵׂה לְהַפְרִישׁ מִמֶּנּוּ רֵאשִׁית לַכֹּהֵן שֶׁנֶּאֱמַר (דברים יח ד) "רֵאשִׁית דְּגָנְךָ תִּירשְׁךָ וְיִצְהָרֶךָ" (דברים יח ד) "תִּתֶּן לּוֹ". מַה דָּגָן תִּירוֹשׁ וְיִצְהָר מַאֲכַל בְּנֵי אָדָם וְגִדּוּלָיו מִן הָאָרֶץ וְיֵשׁ לוֹ בְּעָלִים שֶׁנֶּאֱמַר דְּגָנְךָ אַף כָּל כַּיּוֹצֵא בָּהֶן חַיָּב בִּתְרוּמוֹת וְכֵן בְּמַעַשְׂרוֹת:
כסף משנה
1.
[We are] obligated [to separate] terumah from food1To exclude herbs grown as dyes and the like. This is derived from the fact that the prooftext cited states: "And you shall eat" [the Rambam's Commentary to the Mishnah (Ma'aserot 1:1)]. [designated] for human [consumption],2In contrast to animal fodder (Shabbat 68a). that is guarded,3By its owner, rather than left ownerless (the Rambam's Commentary to the Mishnah, loc. cit.). and that grows from the earth.4This excludes mushrooms whose roots do not enter the earth. It is a positive commandment5Sefer HaMitzvot (positive commandment 126) and Sefer HaChinuch (mitzvah 507) include this commandment among the 613 mitzvot of the Torah. to separate the first portion [of such crops] for a priest, as [Deuteronomy 18:4] states: "You shall give him the first portion of your grain, your wine, and your oil." Just as grain, wine, and oil are [agricultural produce that] is food that is designated for humans, grows from the earth, and has an owner - as indicated by the term "your grain,"6I.e., grain that someone calls his own. - so, too, [we are] obligated to [separate] terumot and tithes from any analogous [agricultural produce].7I.e., the Rambam considers grain, wine, and oil as examples, teaching that all similar produce must be tithes. Other commentaries (the Ra'avad, gloss to Hilchot Ma'aser 1:9; Rashi, Berachot 36a) maintain that, according to Scriptural Law, we are obligated to separate terumot and the tithes from only these three types of produce. They maintain that the obligation to separate the tithes from other types of produce is Rabbinic in origin. See also Halachah 6.

הלכה ב
הַכַּרְשִׁינִין אַף עַל פִּי שֶׁאֵינָם מַאֲכַל אָדָם הוֹאִיל וְאוֹכְלִין אוֹתָן בִּשְׁנֵי רְעָבוֹן חַיָּבִין בִּתְרוּמָה וּמַעַשְׂרוֹת. הַסִּיאָה וְהָאֵזוֹב וְהַקּוֹרָנִית שֶׁזְּרָעָן מִתְּחִלָּה לְאָדָם חַיָּבִין בְּמַעֲשֵׂר. וְכֵן כָּל כַּיּוֹצֵא בָּהֶן. זְרָעָן לְמַאֲכַל בְּהֵמָה אַף עַל פִּי שֶׁנִּמְלַךְ וְחִשֵּׁב עֲלֵיהֶן לְאָדָם כְּשֶׁהֵן מְחֻבָּרִין פְּטוּרִין שֶׁמַּחְשֶׁבֶת חִבּוּר אֵינָהּ כְּלוּם. עָלוּ מֵאֲלֵיהֶן בֶּחָצֵר. אִם הִיא חָצֵר הַמְשַׁמֶּרֶת פֵּרוֹתֶיהָ הֲרֵי אֵלּוּ חַיָּבִין שֶׁסְּתָמָן לְאָדָם וְאִם אֵינָהּ מְשַׁמֶּרֶת פֵּרוֹתֶיהָ פְּטוּרָה:
כסף משנה
2.
[We are] obligated [to separate] terumah and tithes from vetch,8Beans that are used as animal fodder. even though it is not [usually] food for humans, since it is eaten [by humans] in a year of famine. [We are] obligated [to separate] tithes from siyah, hyssop,9This is the common translation for the term aizov. In his notes to the Rambam's Commentary to the Mishnah, Sh'vi'it, ch. 8, note 6, Rav Kappach identifies the Arabic term used by the Rambam as "oregano." and koranit10In his Commentary to the Mishnah (Ma'aserot 3:3), the Rambam identifies these species as types of hyssop that grow wildly in gardens and courtyards. that are sown for human consumption. Similar laws apply to analogous species.
If they were sown as animal fodder, even though the person changed his mind and thought to use them for human [consumption] while they were still connected to the ground, they are exempt. For the intent [of the owner] while [the produce] is growing is of no consequence.11This is a principle applicable in other halachic contexts as well. See Hilchot Tuma'at Ochalin 3:3.
[The following rules apply if] these herbs grow in a courtyard on their own. If the produce growing in the courtyard is guarded,12E.g., it has a fence or the like around it. [we are] obligated to [separate the tithes], for most probably it is for human consumption. If the produce within is not guarded, it is exempt.

הלכה ג
זֵרְעוֹנֵי גִּנָּה שֶׁאֵינָן נֶאֱכָלִים כְּגוֹן זֶרַע לֶפֶת וְזֶרַע צְנוֹן וְזֶרַע בְּצָלִים וְכַיּוֹצֵא בָּהֶן פְּטוּרִים מִן הַתְּרוּמָה וּמִן הַמַּעַשְׂרוֹת מִפְּנֵי שֶׁאֵינָן אֹכֶל אָדָם. אֲבָל הַקֶּצַח חַיָּב בִּתְרוּמָה וּבְמַעַשְׂרוֹת:
כסף משנה
3.
Seeds of garden vegetables that are not eaten, e.g., turnip seed, raddish seed, onion seed, and the like are exempt from terumah and tithes, because they are not used for human consumption. [We are,] by contrast, obligated [to separate] terumah and tithes from caraway seed.13For it is used for human consumption. The Radbaz maintains that the obligation is Scriptural in origin.

הלכה ד
תְּמָרוֹת שֶׁל תִּלְתָּן וְשֶׁל חַרְדָּל וְשֶׁל פּוֹל הַלָּבָן וְשֶׁל צָלָף וְהַקַּפְרִיסִין שֶׁל צָלָף פְּטוּרִים מִפְּנֵי שֶׁאֵינָן פְּרִי. בַּמֶּה דְּבָרִים אֲמוּרִים בְּשֶׁזְּרָעָן לְזֶרַע. אֲבָל זְרָעָן לְיָרָק הֲרֵי אֵלּוּ חַיָּבִים. וְכֵן הָאֶבְיוֹנוֹת שֶׁל צָלָף חַיָּבִים מִפְּנֵי שֶׁהֵן פְּרִי:
כסף משנה
4.
Blossoms of chilba,14A pungent herb. mustard seed, white beans, capers, and the caper bark15Our translation is taken from the Rambam's Commentary to the Mishnah (Ma'aserot 4:6). are exempt, because they are not considered as produce.
When does the above apply? When they were sown for seed. When, however, they were sown for their produce, there is an obligation [to tithe].16The Radbaz maintains that the obligation is Rabbinic in origin. Similarly, there is an obligation [to tithe] caper berries, because they are produce.

הלכה ה
כֻּסְבַּר שֶׁזְּרָעָהּ לְזֶרַע יָרָק פָּטוּר מִן הַתְּרוּמָה וּמִן הַמַּעַשְׂרוֹת. זְרָעָהּ לְיָרָק מַפְרִישׁ תְּרוּמוֹת וּמַעַשְׂרוֹת מִן הַיְרָקוֹת וּמִן הַזֶּרַע. וְכֵן הַשֶּׁבֶת שֶׁזְּרָעָהּ לִזְרֹעַ יַרְקָהּ פָּטוּר. זְרָעָהּ לְיָרָק מִתְעַשֶּׂרֶת זֶרַע וְיָרָק. וְאֵינָהּ מִתְעַשֶּׂרֶת זִרִין. זְרָעָהּ לְזִרִין מַפְרִישׁ תְּרוּמָה וּמַעַשְׂרוֹת מִן הַזֶּרַע וּמִן הַיָּרָק וּמִן הַזִּרִין. וְכֵן הַשִּׁחֲלַיִם וְהַגַּרְגֵּר שֶׁזְּרָעָן לְזֶרַע מִתְעַשְּׂרִין זֶרַע וְיָרָק. כֵּיצַד מִתְעַשְּׂרִין לְזֶרַע וּלְיָרָק. שֶׁאִם לִקֵּט הַיָּרָק לְאָכְלוֹ מַפְרִישׁ תְּרוּמָה וּמַעַשְׂרוֹת וְאַחַר כָּךְ יֹאכַל. וּכְשֶׁיִּיבַשׁ וְיֶאֱסֹף הַזֶּרַע שֶׁלּוֹ מַפְרִישׁ מִן הַזֶּרַע:
כסף משנה
5.
When coriander was sown for seed, its vegetable is exempt from terumah and the tithes.17Since it was sown as seed, the vegetables that grow are of no consequence. If it was sown as a vegetable, we must separate terumot and tithes from both the vegetables and the seed.18For even the seed can be used for human consumption. Similarly, when shevet19In his notes to the Rambam's Commentary to the Mishnah (Pe'ah, ch. 3, note 4), Rav Kappach identifies this as dill. is sown for seed, its vegetable is exempt from terumah and the tithes. If it was sown as a vegetable, we must separate terumot and tithes from both the vegetables and the seed. The seed capsules need not be tithed. If he sowed it for the sake of the seed capsules, he must separate terumot and tithes from the vegetables, the seed, and the seed capsules. Similarly, when cress and wild cress20See Rav Kappach's Commentary to the Mishnah (Ma'aserot 4:5). were sown as a vegetable, we must separate tithes from both the seed and the vegetables.
What is meant by [the statement] we must separate tithes from both the seed and the vegetables? That if he gathered the vegetables to eat them, he must separate terumah and the tithes and [only] then, eat. When [he allows the plant] to dry [and produce] seeds which he gathers, he must make these separations from the seed.

הלכה ו
הַיְרָקוֹת אַף עַל פִּי שֶׁהֵן מַאֲכַל אָדָם אֵינָן חַיָּבִין בְּמַעַשְׂרוֹת אֶלָּא מִדִּבְרֵיהֶן. לְפִי שֶׁנֶּאֱמַר בְּמַעֲשֵׂר (דברים יד כב) "תְּבוּאַת זַרְעֶךָ". תְּבוּאָה וְכַיּוֹצֵא בָּהּ. אֲבָל הַיְרָקוֹת אֵינָן בִּכְלַל הַתְּבוּאָה. וְכֵן יֵרָאֶה לִי שֶׁהוּא הַדִּין בִּתְרוּמָה. שֶׁהֲרֵי נֶאֱמַר בָּהּ (דברים יח ד) "דְּגָנְךָ תִּירשְׁךָ וְיִצְהָרֶךָ" כָּל הַדּוֹמֶה לְאֵלּוּ אֲבָל תְּרוּמַת הַיָּרָק מִדִּבְרֵיהֶם כְּמַעֲשֵׂר:
כסף משנה
6.
Even though vegetables are used for human consumption, the obligation to tithe them is only Rabbinic in origin.21The obligation to make these separations from other fruits, by contrast, is Scriptural in origin. See Halachah 1 and notes. [The rationale is that] with regard to the tithes, [Deuteronomy 14:22] speaks of "the yield of your planting." Now the term tevuah [translated as "yield"] refers to grain and the like. Vegetables are not included as tevuah.
Similarly, it appears to me22The Rambam's use of this expression in this instance has raised questions. Generally, he employs this expression to refer to laws that he derives through his powers of deduction without a previous Rabbinic source. In this instance, however, this concept is explicitly stated in the Jerusalem Talmud (Challah 4:4) and in the Babylonian Talmud (Zevachim 76a). that this also applies with regard to terumah, for with regard to terumah, it is stated: "your grain, your wine, and your oil." Implied is that the obligation is applied to all species resembling those.23And vegetables are not comparable to these species. Instead, terumah which is separated from vegetables is a Rabbinic decree like their tithes.

הלכה ז
אֵין מַפְרִישִׁין תְּרוּמוֹת וּמַעַשְׂרוֹת מִן הַיָּרָק בְּחוּצָה לָאָרֶץ. וַאֲפִלּוּ בִּמְקוֹמוֹת שֶׁאָמַרְנוּ שֶׁמַּפְרִישִׁין בָּהֶן מַעַשְׂרוֹת. וְכֵן יָרָק הַבָּא מִחוּצָה לָאָרֶץ לָאָרֶץ אַף עַל פִּי שֶׁיֵּשׁ עָפָר בְּעִקָּרֶיהָ הֲרֵי זֶה פָּטוּר וְלֹא גָּזְרוּ עָלָיו. הַתְּבוּאָה וְהַקִּטְנִית שֶׁזְּרָעָן לְיָרָק בָּטְלָה דַּעְתּוֹ אֵצֶל כָּל אָדָם. וְהַיָּרָק שֶׁלָּהֶן פָּטוּר. וְהַזֶּרַע חַיָּב בִּתְרוּמָה וּמַעַשְׂרוֹת:
כסף משנה
7.
We do not separate terumah and tithes from vegetables in the Diaspora, even in the places where we said that tithes should be separated,24See Chapter 1, Halachah 1, which states that tithes should be separated in Babylon, Ammon and Moab. Nevertheless, since there is no Scriptural obligation to tithe vegetable, our Sages did not impose such an obligation in the Diaspora. Thus even when vegetables from Eretz Yisrael are exported to the Diaspora in contemporary times, there is no need to separate terumah and tithes. Similarly, vegetables that come from the Diaspora to Eretz Yisrael, even though there is earth in their roots,25And thus they will continue growing in Eretz Yisrael. they are exempt26According to Scriptural Law. Even though there is an obligation on other produce as stated in Chapter 1, Halachah 22, our Sages did not extend this obligation to vegetables. and nothing was decreed concerning them.27By the Sages.
When grain or legumes are sown for their vegetables, the person's intent is not considered of consequence because of the prevailing conception of most people. [Hence,] their vegetables are exempt and [we are] obligated [to separate] terumah and tithes from their kernels.

הלכה ח
הַתִּלְתָּן אַף עַל פִּי שֶׁאֵינוֹ אֹכֶל אָדָם כְּשֶׁיִּקְשׁוּ הוֹאִיל וְרֹב הָאָדָם אוֹכְלִין אוֹתָן בִּתְחִלָּתָן הֲרֵי הֵן חַיָּבִין בִּתְרוּמָה וּמַעֲשֵׂר:
כסף משנה
8.
Even though tiltan28An herb identified as chilbah, a sharp and pungent herb used in Eretz Yisrael today. is not considered as fit for human consumption when it becomes hard,29And thus there are certain laws (see Chapter 11, Halachah 9; Chapter 12, Halachah 7) that deal with chilbah as if it were not fit for human consumption. since most people eat it at the beginning [of its development],30When it is still soft and edible. [we are] obligated [to separate] terumah and tithes from it.31The Ra'avad takes issue with the Rambam, noting that in Halachah 4, he ruled that chilbah blossoms are exempt. The Kessef Mishneh explains that there is no contradiction, for there is a difference between chilbah and chilbah blossoms.

הלכה ט
וְאֵלּוּ פְּטוּרִין מִן הַתְּרוּמָה וּמִן הַמַּעַשְׂרוֹת. הַלֶּקֶט וְהַשִּׁכְחָה וְהַפֵּאָה וְהַפֶּרֶט וְהָעוֹלֵלוֹת. אֲפִלּוּ הֶעֱמִיד מֵהֶן כְּרִי. וְאִם עָשָׂה מֵהֶן גֹּרֶן בַּשָּׂדֶה הֻקְבְּעוּ לְמַעַשְׂרוֹת וּמַפְרִישׁ מֵהֶן תְּרוּמָה וּמַעַשְׂרוֹת. אֲבָל אִם עָשָׂה הַגֹּרֶן בָּעִיר פְּטוּרִין. שֶׁהֲרֵי קוֹל יֵשׁ לָהֶן שֶׁהַכּל יוֹדְעִין שֶׁהֵן לֶקֶט אוֹ שִׁכְחָה אוֹ פֵּאָה:
כסף משנה
9.
The following are exempt from terumah and tithes: Leket, shichachah, pe'ah, individual grapes that separate from a cluster, and underdeveloped grape clusters.32As explained in Hilchot Matanot Aniyim, all of these are portions of one's crops that must be given to the poor. Since they are ownerless, they are exempt according to Scriptural Law, as indicated by Halachah 1.
The Rambam's statements are based on Challah 1:3. That mishnah does not, however, mention individual grapes that separate from a cluster and underdeveloped grape clusters. Nevertheless, since they are also presents given to the poor from our produce, the same laws apply to them.
This applies even if [a poor person] collects them in a grainheap.33Although the Jerusalem Talmud (Kilayim 6:2) equates a granary with a grainheap, the Babylonian Talmud (Berachot 40b) mentions only a granary (Kessef Mishneh). If, however, he collects them in a granary in the field, it is established that there is an obligation for tithes upon them and terumah and tithes must be separated from them.34As evident from the continuation of the Rambam's statements, the obligation is Rabbinic in origin, lest an observer think that the harvesting process will have been completed by the owner of the field without the agricultural obligations being met. See Berachot, loc. cit. If, however, he collects them in a granary in a town, they are exempt, for the matter is spoken about and everyone knows that [the produce] is leket, shichachah, and pe'ah.

הלכה י
הַלֶּקֶט וְהַשִּׁכְחָה וְהַפֵּאָה שֶׁל עַכּוּ''ם חַיָּבִין בִּתְרוּמָה וּמַעַשְׂרוֹת. אֶלָּא אִם כֵּן הִפְקִיר. וְכֵן הַתְּבוּאָה וְהַזֵּיתִים שֶׁלֹּא הֵבִיאוּ שְׁלִישׁ פְּטוּרִין מִן הַתְּרוּמָה וּמִן הַמַּעַשְׂרוֹת. וּמִנַּיִן יוֹדֵעַ. כָּל שֶׁזּוֹרְעָהּ וּמַצְמַחַת בְּיָדוּעַ שֶׁהֵבִיאָה שְׁלִישׁ. עָבַר וְהִפְרִישׁ מִתְּבוּאָה וְזֵיתִים שֶׁלֹּא הֵבִיאוּ שְׁלִישׁ אֵינָהּ תְּרוּמָה:
כסף משנה
10.
One is obligated [to separate] terumah and tithes from leket, shichachah, and pe'ah [left] by a gentile35A gentile is not required to leave these presents for the poor. Hence, if he does leave them, they are not given that status. Nevertheless, they are not considered as ownerless, but rather as a present given by the gentile to the poor (Radbaz). Hence, the produce is considered as produce from a gentile acquired by a Jew. If the Jew completes the work associated with the produce, terumah and the tithes must be separated from it [Chapter 1, Halachot 10-11; see also the Rambam's Commentary to the Mishnah (Pe'ah 4:9)]. unless he declared them ownerless. Similarly, if grain and olives did not reach a third of their growth, they are exempt from terumah and the tithes.36Because the produce is not considered significant until it reaches that size (Siftei Cohen 331:28).
How can one know [whether produce has reached a third of its growth]? When [the kernels] would grow if they were sown,37Our translation is based on the Rambam's Commentary to the Mishnah (Ma'aserot 1:3). it is known that it has reached a third of its growth. If a person transgressed and separated [terumah] from grain and olives before they reached a third of their growth, [the separated produce] is not terumah.38If a separation was made from produce that was exempt for produce that was liable, a new separation must be made and none of the prohibitions applying to terumah are associated with the produce separated originally.

הלכה יא
וְכֵן הַהֶפְקֵר פָּטוּר מִן הַתְּרוּמָה וּמִן הַמַּעַשְׂרוֹת. וַאֲפִלּוּ הִפְקִירוֹ הָעַכּוּ''ם לוֹ. אֲבָל הַזּוֹרֵעַ שְׂדֵה הֶפְקֵר חַיָּב בִּתְרוּמָה וּמַעַשְׂרוֹת:
כסף משנה
11.
Similarly, produce that is declared ownerless is exempt from terumah and tithes. [This applies also to produce] declared ownerless by a gentile.39Although declaring property ownerless is in certain matters equivalent to taking a vow (Hilchot Nedarim 2:14) and the laws of vows do not apply to a gentile, when a gentile declares property ownerless, his declaration is effective. This concept is not accepted by all authorities and some even suggest alternate versions of the Mishneh Torah. Nevertheless, it is borne out by the Rambam's Commentary to the Mishnah (Pe'ah, loc. cit.). Nevertheless, if one planted [crops] on a field that was declared ownerless, he is obligated [to separate] terumah and tithes [from the crops].40For the crops themselves are not ownerless (Radbaz).

הלכה יב
הִפְקִיר קָמָה וְזָכָה בָּהּ וְעָבַר וְהִפְרִישׁ מִמֶּנָּה תְּרוּמָה הֲרֵי זוֹ תְּרוּמָה. אֲבָל אִם הִפְקִיר שִׁבֳּלִים וְזָכָה בָּהֶן וְעָבַר וְהִפְרִישׁ מֵהֶן תְּרוּמָה אֵינָהּ תְּרוּמָה. וְכֵן כָּל הַמַּפְרִישׁ מִדָּבָר שֶׁאֵינוֹ חַיָּב תְּרוּמָה אֵינָהּ תְּרוּמָה. וְכֵן בְּמַעַשְׂרוֹת. דְּבָרִים שֶׁאֵין דֶּרֶךְ רֹב בְּנֵי אָדָם לְזָרְעָן בַּגִּנּוֹת וּבַשָּׂדוֹת אֶלָּא חֶזְקָתָן מִן הַהֶפְקֵר פְּטוּרִין מִן הַתְּרוּמָה וּמִן הַמַּעַשְׂרוֹת. כְּגוֹן הַשּׁוּם בַּעַל בֶּכִי. וּבָצָל שֶׁל רִכְפָּה. וּגְרִיס הַקִּלְקְלִי. וַעֲדָשִׁים הַמִּצְרִיּוֹת וְכַיּוֹצֵא בָּהֶן:
כסף משנה
12.
When a person declares standing grain ownerless, takes possession of it, and then transgresses and separates terumah,41He is considered to have transgressed, because, according to law, there is no obligation to separate terumah from such produce. Even though the original owner himself took possession of the field, there is no difference between it and other ownerless crops. See Hilchot Matanot Aniyim 5:27. the laws of terumah apply to the produce separated.42Since while the grain is standing, separating a portion as terumah would not be effective, if it was declared ownerless at that time, that declaration does not prevent the separation of terumah afterwards from being effective [Jerusalem Talmud (Ma'aserot 1:1)]. If, however, he declared sheaves [of grain] ownerless, takes possession of them, and transgresses and separates terumah, the laws of terumah do not apply to the produce separated.43Since terumah separated from sheaves is effective (even though all the work associated with preparing crops is not completed), if the sheaves are declared ownerless, that declaration prevents the separation of terumah from being effective (ibid.). Similarly, whenever a person separates [terumah] from produce from which terumah is not obligated to be separated, the laws of terumah do not apply to the produce separated.
Similarly, with regard to tithes, produce which the majority of people do not ordinarily sow in their gardens and fields, but instead, can be assumed to have grown ownerless are exempt from terumah and tithes. [This includes] garlic that makes one cry, onions of Rikpah,44Our translation is based on the Rambam's Commentary to the Mishnah (Ma'aserot 5:7) where he explains that these species of garlic and onion are so pungent that they cause people to cry. He does, however, allow for the possibility that the Hebrew terms refer to names of places. a pearled Cilcilian bean, Egyptian lentils,45These types of beans and lentils are of abnormal shape and grow wild (ibid.). and the like.

הלכה יג
נִתְעָרֵב דָּבָר שֶׁחַיָּב בִּתְרוּמָה בְּדָבָר שֶׁאֵינוֹ חַיָּב. כְּגוֹן זֵיתֵי נִקּוּף שֶׁנִּתְעָרְבוּ בְּזֵיתֵי מָסִיק וְעִנְבֵי עוֹלֵלוֹת בְּעִנְבֵי בָּצִיר. אִם יֵשׁ לוֹ פֵּרוֹת אֲחֵרוֹת מוֹצִיא עַל הַחַיָּב לְפִי חֶשְׁבּוֹן. וְאִם אֵין לוֹ אֶלָּא אֵלּוּ מַפְרִישׁ תְּרוּמָה וּתְרוּמַת מַעֲשֵׂר עַל הַכּל וּכְאִלּוּ הַכּל חַיָּב בִּתְרוּמָה. וּמַפְרִישׁ מַעֲשֵׂר רִאשׁוֹן וְשֵׁנִי לְפִי חֶשְׁבּוֹן דָּבָר הַחַיָּב:
כסף משנה
13.
[The following laws apply if] produce from which we are obligated to separate terumah becomes mixed with produce which is exempt,46And a separation between the two cannot be made. e.g., olives gathered by the poor47From which terumah need not be separated. become mixed with olives reaped [by the owner], underdeveloped grape clusters48These types of beans and lentils are of abnormal shape and grow wild (ibid.). become mixed with grapes that were harvested. If the person has other produce,49From which he is obligated to separate terumah, but from which he did not separate it as of yet. he separates [terumah from it] for the produce upon which the obligation lies according to the appropriate reckoning.50I.e., if five pounds of grapes from which there was an obligation to separate terumah become mixed with other grapes, we separate an amount of terumah sufficient for five pounds of grapes from an additional source of grapes. With regard to the measure of terumah appropriate to give, see the following chapter. If this is all the produce the person has, he should separate terumah and terumat ma'aser for the entire mixture,51This is speaking about an instance where wine was made from the grapes and oil from the olives. Hence every drop contains a mixture of produce from which terumah is obligated to be separated and produce upon which there is no obligation. as if there was an obligation to separate terumah from the entire amount.52He cannot merely separate the appropriate amount from the mixture, because one may not separate terumah (or tithes) from produce upon which there is no obligation for produce upon which there is an obligation. Since in every drop that he separates, there is a portion upon which there is no obligation, that separation is not effective (Siftei Cohen 331:28). As the Rambam writes in his Commentary to the Mishnah (Challah 3:9), one must be stringent and separate terumah and terumat ma'aser for the entire amount, because one is liable for death at the hand of heaven for partaking of produce from which these allocations were not made properly.
In that source, the Rambam adds that the owner must buy the olives or the grapes to be given to the poor from them before he takes possession of the entire mixture.
He should separate the first and second tithes for the produce upon which the obligation lies according to the appropriate reckoning.53The Siftei Cohen 331:29 and the Turei Zahav 331:7 explain that the intent is that one should separate the tithes for the entire amount, but give the Levite only the tithe for the amount upon which the obligation originally lay. In this manner, he will not have separated the tithes from produce upon which there is no obligation and yet will not have given the Levite more than would have had to.

הלכה יד
הַתְּרוּמָה לַכֹּהֵן בֵּין טְהוֹרָה בֵּין טְמֵאָה אֲפִלּוּ נִטְמָא הַדָּגָן אוֹ הַתִּירוֹשׁ כֻּלּוֹ קֹדֶם שֶׁיַּפְרִישׁ הֲרֵי זֶה חַיָּב לְהַפְרִישׁ מִמֶּנּוּ תְּרוּמָה בְּטֻמְאָה וְלִתְּנָהּ לַכֹּהֵן שֶׁנֶּאֱמַר (במדבר יח ח) "וַאֲנִי נָתַתִּי לְךָ אֶת מִשְׁמֶרֶת תְּרוּמֹתָי", אַחַת טְהוֹרָה וְאַחַת טְמֵאָה. הַטְּהוֹרָה נֶאֱכֶלֶת לַכֹּהֲנִים וְהַטְּמֵאָה יֵהָנוּ בִּשְׂרֵפָתָהּ. אִם הָיָה שֶׁמֶן מַדְלִיקִין אוֹתוֹ. וְאִם הָיָה דָּגָן וְכַיּוֹצֵא בּוֹ מַסִּיקִין בּוֹ אֶת הַתַּנּוּר:
כסף משנה
14.
Terumah [must be given] to a priest whether it is in a state of ritual purity or not. Even if all the grain or the wine became impure before [terumah] was separated, he is obligated to separate the terumah that is impure and give it to a priest, as [Numbers 18:8] states: "And behold I have given you the watch over My terumah,"54In the verse, the noun terumah uses a plural form alluding to two types of terumah: pure terumah and impure terumah. See also Hilchot Ma'aser 6:2. i.e., whether it is pure or impure. The pure [terumah] may be eaten by the priests and they can benefit from the impure [terumah] by burning it.55It is forbidden to partake of it. If it is oil, it can be kindled [as fuel for a lamp]. If it is grain or the like, it can be used as fuel for an oven.56It may not, however, be given to animals as animal fodder. See Sefer HaMitzvot (positive commandment 90) which states that it is a mitzvah to burn impure terumah. Impure terumah from fruits that will not be useful as fuel must be buried.

הלכה טו
וְכֵן תְּרוּמַת מַעֲשֵׂר אִם נִטְמֵאת אוֹ נִטְמָא הַמַּעֲשֵׂר מַפְרִישִׁין אוֹתָהּ בְּטֻמְאָה וְנִתֶּנֶת לַכֹּהֵן לֵהָנוֹת בִּשְׂרֵפָתָהּ:
כסף משנה
15.
Similarly, if terumat ma'aser became impure - or if the tithes became impure, he must separate [terumat ma'aser] in impurity and give it to a priest to benefit from by using it as fuel.

הלכה טז
וְכָל הַמַּפְרִישׁ תְּרוּמָה גְּדוֹלָה אוֹ תְּרוּמַת מַעֲשֵׂר מְבָרֵךְ קֹדֶם שֶׁיַּפְרִישׁ כְּדֶרֶךְ שֶׁמְּבָרְכִין עַל כָּל הַמִּצְוֹת כְּמוֹ שֶׁבֵּאַרְנוּ בִּבְרָכוֹת:
כסף משנה
16.
Anyone who separates the great terumah or terumat ma'aser should recite a blessing before separating it, just as one recites a blessing over the observance of all the mitzvot, as we explained in [Hilchot] Berachot.57As stated in Hilchot Berachot 11:2, 6, 12, a blessing should be recited before the observance of every positive commandment.

הלכה יז
אֵין מוֹצִיאִין תְּרוּמָה מֵהָאָרֶץ לְחוּצָה לָאָרֶץ אֲפִלּוּ טְמֵאָה. וְאֵין מְבִיאִין תְּרוּמָה מִחוּצָה לָאָרֶץ לָאָרֶץ. וְאִם הֵבִיא לֹא תֵּאָכֵל מִפְּנֵי שֶׁהִיא טְמֵאָה בְּאֶרֶץ הַכּוּתִים. וְלֹא תִּשָּׂרֵף שֶׁלֹּא יֹאמְרוּ רָאִינוּ תְּרוּמָה שֶׁלֹּא נִטְמֵאת נִשְׂרֶפֶת. וְלֹא תַּחֲזֹר לְחוּצָה לָאָרֶץ שֶׁמָּא יֹאמְרוּ מוֹצִיאִין תְּרוּמָה לְחוּצָה לָאָרֶץ. אֶלָּא מַנִּיחִין אוֹתָהּ עַד שֶׁתִּטָּמֵא טֻמְאָה יְדוּעָה לַכּל אוֹ עַד שֶׁיָּבוֹא עֶרֶב הַפֶּסַח אִם הָיְתָה חָמֵץ וְתִשָּׂרֵף:
כסף משנה
17.
Terumah - even impure terumah - should not be taken from Eretz Yisrael to the Diaspora.58If the terumah is pure, it should not be taken to the Diaspora, because the very earth of the Diaspora is considered as impure by Rabbinic decree (see Hilchot Tuma'at Meit, ch. 11) and the terumah will become impure. Even if the terumah was already impure, it should be burnt in Eretz Yisrael. See Sh'vi'it 6:5. We should not bring terumah from the Diaspora to Eretz Yisrael.59Lest the priests seek to leave Eretz Yisrael to collect it [Jerusalem Talmud (Sh'vi'it 6:6)]. If it was brought [from the Diaspora], it should not be eaten, because it is impure because [of contact with] the earth of the nations.60I.e., by Rabbinic decree. It should not be burnt, lest people say: "We saw terumah that did not become impure being burnt." It should not be returned to the Diaspora, lest people say: "Terumah may be taken [from Eretz Yisrael] to the Diaspora." Instead, we leave it until it becomes impure because of a known source of impurity61i.e., it is forbidden in the Diaspora, because of the doubt that perhaps it came into contact with a corpse. Nevertheless, we do not burn it until we know certainly that it became impure. or until the day before Pesach if it was leaven,62For all leaven must be burnt at this time. and then it will be burnt.

זרעים הלכות תרומות פרק ב
Zeraim Terumos Chapter 2