Reference for Terumot 9:3
וְחַיֶּבֶת בְּמַעַשְׂרוֹת וּבְמַעֲשַׂר עָנִי, וַעֲנִיֵּי יִשְׂרָאֵל וַעֲנִיֵּי כֹהֲנִים נוֹטְלִים, וַעֲנִיֵּי יִשְׂרָאֵל מוֹכְרִין אֶת שֶׁלָּהֶם לְכֹהֲנִים בִּדְמֵי תְרוּמָה, וְהַדָּמִים שֶׁלָּהֶם. הַחוֹבֵט מְשֻׁבָּח. וְהַדָּשׁ כֵּיצַד יַעֲשֶׂה, תּוֹלֶה כְפִיפוֹת בְּצַוְּארֵי בְהֵמָה וְנוֹתֵן לְתוֹכָן מֵאוֹתוֹ הַמִּין, נִמְצָא לֹא זוֹמֵם אֶת הַבְּהֵמָה וְלֹא מַאֲכִיל אֶת הַתְּרוּמָה:
And [<i>Terumah</i> that has been planted is] obligated in tithes and the poor man’s tithe. The poor of the Israelites and the poor of the priests may take them, but the poor of the Israelites must sell theirs to the priests for the price of <i>Terumah</i> and the money is theirs. He who beats [the grain with sticks] is praiseworthy. But he who threshes it [with an animal], how should he do it? He should suspend baskets from the neck of the animal and place in them [grain] from the same kind [as that being threshed], with the result that he will neither muzzle the animal nor feed [it] the <i>Terumah</i>.