Reference for Demai 3:6
הַנּוֹתֵן לַחֲמוֹתוֹ, מְעַשֵּׂר אֶת שֶׁהוּא נוֹתֵן לָהּ, וְאֶת שֶׁהוּא נוֹטֵל מִמֶּנָּה, מִפְּנֵי שֶׁהִיא חֲשׁוּדָה לַחֲלֹף אֶת הַמִּתְקַלְקֵל. אָמַר רַבִּי יְהוּדָה, רוֹצָה הִיא בְתַקָּנַת בִּתָּהּ וּבוֹשָׁה מֵחֲתָנָהּ. מוֹדֶה רַבִּי יְהוּדָה בְּנוֹתֵן לַחֲמוֹתוֹ שְׁבִיעִית, שֶׁאֵינָהּ חֲשׁוּדָה לְהַחֲלִיף לְהַאֲכִיל אֶת בִּתָּהּ שְׁבִיעִית:
One who gives his [tithed produce] to his mother-in-law, must tithe from what he gives to her and from what he receives [back] from her because she is suspected of exchanging what is spoiled. Said Rabbi Yehudah, "She desires the well-being of her daughter and is ashamed before her son-in-law." Rabbi Yehudah acknowledges in [the instance of] giving Sabbatical produce to his mother-in-law, that she is not suspected [of exchanging] to feed her daughter Sabbatical year produce.