Reference for Bava Metzia 9:10

הַמְקַבֵּל שָׂדֶה מֵחֲבֵרוֹ לְשָׁבוּעַ אַחַת בִּשְׁבַע מֵאוֹת זוּז, הַשְּׁבִיעִית מִן הַמִּנְיָן. קִבְּלָהּ הֵימֶנּוּ שֶׁבַע שָׁנִים בִּשְׁבַע מֵאוֹת זוּז, אֵין הַשְּׁבִיעִית מִן הַמִּנְיָן:

If one received a field from his neighbor for one seven-year period for seven hundred zuz, the shemitah year (in which the field must lie fallow) is included. If he received it from him for seven years for seven hundred zuz, the shemitah year is not included (and he has it for another "productive" year).

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