Reference for Sheviit 5:6
אֵלּוּ כֵלִים שֶׁאֵין הָאֻמָּן רַשַּׁאי לְמָכְרָם בַּשְּׁבִיעִית, מַחֲרֵשָׁה וְכָל כֵּלֶיהָ, הָעוֹל, וְהַמִּזְרֶה, וְהַדָּקָר. אֲבָל מוֹכֵר הוּא מַגַּל יָד וּמַגַּל קָצִיר, וַעֲגָלָה וְכָל כֵּלֶיהָ. זֶה הַכְּלָל, כָּל שֶׁמְּלַאכְתּוֹ מְיֻחֶדֶת לַעֲבֵרָה, אָסוּר. לְאִסּוּר וּלְהֶתֵּר, מֻתָּר:
These are the tools that a craftsman is not allowed to sell during the Sabbatical year: a plow and all its tools, a yoke, a winnowing fan, and a pick. However, one may sell a hand-sickle, a harvesting sickle, and a wagon and all its tools. This is the rule: anything whose usage is directed toward [work which is a Sabbatical] transgression is forbidden; but [anything the normal usage of which is for work which is] a transgression [on the Sabbatical year] or permitted, it is permitted.