Mishnah Uktzin 3:5: Costus and amomum [various fragrant spices], and choice spices, crowfoot, and asafoetida, or peppers, or saffron bundles may [all] be purchased with [second] tithe money [i.e. they are treated like foods, since money for the second tithe may only be used to purchase food, which must then be consumed in Jerusalem], but they cannot be rendered impure with the impurity of foods, according to Rabbi Akiva. Rabbi Yochanan ben Nuri said to him, "If they may be purchased with [second] tithe money, why then can they not be rendered impure with the impurity of foods? And if they cannot be rendered impure with the impurity of foods, then they too should not be purchased with [second] tithe money!"

הַקֹּשְׁטְ, וְהַחֶמֶס, וְרָאשֵׁי בְשָׂמִים, הַתִּיאָה, וְהַחִלְתִּית, וְהַפִּלְפְּלִין, וְחַלּוֹת חָרִיעַ, נִלְקָחִים בְּכֶסֶף מַעֲשֵׂר וְאֵינָן מִטַּמְּאִין טֻמְאַת אֳכָלִין, דִּבְרֵי רַבִּי עֲקִיבָא. אָמַר לוֹ רַבִּי יוֹחָנָן בֶּן נוּרִי, אִם נִלְקָחִים בְּכֶסֶף מַעֲשֵׂר, מִפְּנֵי מָה אֵינָן מִטַּמְּאִין טֻמְאַת אֳכָלִין. וְאִם אֵינָן מִטַּמְּאִין טֻמְאַת אֳכָלִים, אַף הֵם לֹא יִלָּקְחוּ בְכֶסֶף מַעֲשֵׂר:

Mishnah Uktzin 3:6: Regarding figs or grapes which are not yet ripe, Rabbi Akiva considers them [susceptible to becoming] impure with the impurity of foods. Rabbi Yochanan ben Nuri says: [they become susceptible to being rendered impure] once they have come to the season of [requiring] tithes. Regarding hardened olives or grapes, Beit Shammai consider them [susceptible to being rendered] impure, and Beit Hillel consider them pure [i.e. insusceptible]. Regarding black cumin, Beit Shammai consider it pure, and Beit Hillel consider it impure. And so too [did they differ] with regard to [its requiring] tithes.

הַפַּגִּין וְהַבֹּסֶר, רַבִּי עֲקִיבָא מְטַמֵּא טֻמְאַת אֳכָלִין. רַבִּי יוֹחָנָן בֶּן נוּרִי אוֹמֵר, מִשֶּׁיָּבֹאוּ לְעוֹנַת הַמַּעַשְׂרוֹת. פְּרִיצֵי זֵיתִים וַעֲנָבִים, בֵּית שַׁמַּאי מְטַמְּאִין וּבֵית הִלֵּל מְטַהֲרִין. הַקֶּצַח, בֵּית שַׁמַּאי מְטַהֲרִין, וּבֵית הִלֵּל מְטַמְּאִין. וְכֵן לַמַּעַשְׂרוֹת: