"If a man steals an ox or a sheep" (Exodus 21:37). Even the one who slaughters and the one who sells were already included in the general rule, as it says, "if the thief is found" (Exodus 22:6). Yet Scripture removes him from the general rule to be stringent with him, that he should pay fourfold and fivefold; for this reason the passage was stated. "If a man steals an ox or a sheep" — to make him liable for this one on its own and for that one on its own. "And he slaughtered it" — I have only one who slaughters; from where do I include one who sells? Scripture teaches, "or sold it." Before this is stated, one might say: I have it by reasoning — if the one who slaughters is liable, shall the one who sells not be liable? If you say so, you have imposed a penalty by reasoning. Therefore it is said, "or sold it," to teach you that one does not impose penalties on the strength of reasoning alone.
No Punishment Is Derived by Logic Alone for the Thief
Yalkut Shimoni on Torah 342:1
(שמות כא לז) כִּי יִגְנֹב אִישׁ שׁוֹר אוֹ שֶׂה אַף הַטּוֹבֵחַ וְהַמּוֹכֵר הָיוּ בַּכְּלָל, שֶׁנֶּאֱמַר (שמות כב, ו) "אִם יִמָּצֵא הַגַּנָּב", וַהֲרֵי הַכָּתוּב מוֹצִיאוֹ מִכְּלָלוֹ, לְהַחְמִיר עָלָיו שֶׁיְּשַׁלֵּם תַּשְׁלוּמֵי אַרְבָּעָה וַחֲמִשָּׁה, לְכָךְ נֶאֶמְרָה הַפָּרָשָׁה. כִּי יִגְנֹב אִישׁ שׁוֹר אוֹ שֶׁה, לְחַיֵּב עַל זֶה בִּפְנֵי עַצְמוֹ, וְעַל זֶה בִּפְנֵי עַצְמוֹ. וּטְבָחוֹ, אֵין לִי אֶלָּא טוֹבֵחַ, מוֹכֵר מִנָּיִן, תַּלְמוּד לוֹמַר [אוֹ] (וּ)מְכָרוֹ. עַד שֶׁלֹּא יֹאמַר יֵשׁ לִי בַּדִּין, אִם הַטּוֹבֵחַ חַיָּב, מוֹכֵר לֹא יְהֵא חַיָּב. אִם אֲמַרְתְּ כֵּן, עָנַשְׁתָּ מִן הַדִּין, לְכָךְ נֶאֱמַר [אוֹ] (וּ)מְכָרוֹ, לְלַמֶּדְךָ שֶׁאֵין עוֹנְשִׁין מִן הַדִּין.