Reference for Tahorot 2:2
רַבִּי אֱלִיעֶזֶר אוֹמֵר, הָאוֹכֵל אֹכֶל רִאשׁוֹן, רִאשׁוֹן. אֹכֶל שֵׁנִי, שֵׁנִי. אֹכֶל שְׁלִישִׁי, שְׁלִישִׁי. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, הָאוֹכֵל אֹכֶל רִאשׁוֹן וְאֹכֶל שֵׁנִי, שֵׁנִי. שְׁלִישִׁי, שֵׁנִי לַקֹּדֶשׁ וְלֹא שֵׁנִי לַתְּרוּמָה, בְּחֻלִּין שֶׁנַּעֲשׂוּ לְטָהֳרַת תְּרוּמָה:
Rabbi Eliezer says: One who eats foods of a first degree [level of impurity] is [himself rendered] of a first degree; [if he eats] foods of a second degree, [he is rendered] of a second degree; foods of a third degree, [he is rendered] of a third degree. Rabbi Yehoshua says: One who eats foods of a first degree or of a second degree is [rendered] of a second degree; [one who eats foods] of a third degree, [he is rendered] of second degree for sanctified foods, but not for <i>terumah</i>, [and this applies] with non-sacred food prepared with the purity stringency of <i>terumah</i> [since regular non-sacred foods do not have third degree impurity].