Ma'aser Sheini 5:5
Ma'aser Sheini5: 5
וּבִשְׁבִיעִית, פּוֹדֵהוּ בְשָׁוְיוֹ. וְאִם הָיָה הַכֹּל מֻפְקָר, אֵין לוֹ אֶלָּא שְׂכַר לְקִיטָה. הַפּוֹדֶה נֶטַע רְבָעִי שֶׁלּוֹ, מוֹסִיף עָלָיו חֲמִישִׁיתוֹ, בֵּין שֶׁהוּא שֶׁלּוֹ וּבֵין שֶׁנִּתַּן לוֹ בְמַתָּנָה.
However, in the Shemittah [lit., seventh] year, one redeems it for its worth. And if all of it was ownerless, he is only entitled to the cost of picking.  [If] someone redeems his own fourth-year plantation, he adds to it its fifth, whether it is his [own] or whether it was given to him as a gift.