Reference for Maasrot 2:8
הָיָה עוֹשֶׂה בִלְבָסִים, לֹא יֹאכַל בִּבְנוֹת שֶׁבַע. בִּבְנוֹת שֶׁבַע, לֹא יֹאכַל בִּלְבָסִים. אֲבָל מוֹנֵעַ הוּא אֶת עַצְמוֹ עַד שֶׁמַּגִּיעַ לִמְקוֹם הַיָּפוֹת וְאוֹכֵל. הַמַּחֲלִיף עִם חֲבֵרוֹ, זֶה לֶאֱכֹל וְזֶה לֶאֱכֹל, זֶה לִקְצוֹת וְזֶה לִקְצוֹת, זֶה לֶאֱכֹל וְזֶה לִקְצוֹת, חַיָּב. רַבִּי יְהוּדָה אוֹמֵר, הַמַּחֲלִיף לֶאֱכֹל, חַיָּב, וְלִקְצוֹת, פָּטוּר:
If [a hired worker is] working among bad figs, he may not eat of white figs. If among white figs, he may not eat of bad figs, but must restrain himself until he reaches the place of the better figs, and [there] he may eat. If a man exchanges with his friend, either [figs] to be eaten for [figs] to be eaten, or [figs] to be dried for [figs] to be dried, or [figs] to be eaten for [figs] to be dried, then he is required [to give tithes]. Rabbi Yehudah says: one who exchanges for [figs] to be eaten is required, but [for figs] to be dried is exempt.