Reference for Demai 3:3
הַמּוֹצֵא פֵרוֹת בַּדֶּרֶךְ וּנְטָלָן לְאָכְלָן, וְנִמְלַךְ לְהַצְנִיעַ, לֹא יַצְנִיעַ עַד שֶׁיְּעַשֵּׂר. וְאִם מִתְּחִלָּה נְטָלָן בִּשְׁבִיל שֶׁלֹּא יֹאבֵדוּ, פָּטוּר. כָּל דָּבָר שֶׁאֵין אָדָם רַשַּׁאי לְמָכְרוֹ דְּמַאי, לֹא יִשְׁלַח לַחֲבֵרוֹ דְּמַאי. רַבִּי יוֹסֵי מַתִּיר בְּוַדַּאי, וּבִלְבַד שֶׁיּוֹדִיעֶנּוּ:
Someone who finds produce on the road, and takes them to eat them, but then decides to hide them, should not hide them until he tithes them. If from the start he took them [the produce] so that they should not spoil, they are exempt. Anything which a person is not permitted to sell when it is <i>Demai</i> should also not be sent to a friend when it is <i>Demai</i>. Rabbi Yossi allows this [in a case of] certainly [untithed produce], as long as he informs him.