Reference for Maasrot 2:5
הָאוֹמֵר לַחֲבֵרוֹ, הֵילָךְ אִסָּר זֶה וְתֶן לִי בוֹ חָמֵשׁ תְּאֵנִים, לֹא יֹאכַל עַד שֶׁיְּעַשֵּׂר, דִּבְרֵי רַבִּי מֵאִיר. רַבִּי יְהוּדָה אוֹמֵר, אוֹכֵל אַחַת אַחַת, פָּטוּר, וְאִם צֵרַף, חַיָּב. אָמַר רַבִּי יְהוּדָה, מַעֲשֶׂה בְגִנַּת וְרָדִים שֶׁהָיְתָה בִירוּשָׁלַיִם, וְהָיוּ תְאֵנִים נִמְכָּרוֹת מִשָּׁלֹשׁ וּמֵאַרְבַּע בְּאִסָּר, וְלֹא הֻפְרַשׁ מִמֶּנָּה תְרוּמָה וּמַעֲשֵׂר מֵעוֹלָם:
One who says to his friend: “Here is this <i>Issar</i> [specific unit of money], and give me five figs for it”, he may not eat [of them] until he has tithed [them], the words of Rabbi Meir. Rabbi Yehudah says: if he ate them one by one, he is exempt. If he combined them, he is required [to tithe.] Rabbi Yehudah said: it happened in a rose-garden that was in Jerusalem, and there were figs being sold three or four for an <i>Issar</i>, and neither <i>Terumah</i> nor tithes were ever set aside from it.