אורח חיים קנ״וOrach Chayim 156

Se’if 1א׳

אַחַר כָּךְ יֵלֵךְ לַעֲסָקָיו, דְּכָל תּוֹרָה שֶׁאֵין עִמָּהּ מְלָאכָה סוֹפָהּ בְּטֵלָה וְגוֹרֶרֶת עָוֹן, כִּי הָעֹנִי יַעֲבִירֶנּוּ עַל דַּעַת קוֹנוֹ; וּמִכָּל מָקוֹם לֹא יַעֲשֶׂה מְלַאכְתּוֹ עִקָּר, אֶלָּא עֲרַאי, וְתוֹרָתוֹ קֶבַע, וְזֶה וָזֶה יִתְקַיֵּם בְּיָדוֹ; וְיִשָּׂא וְיִתֵּן בֶּאֱמוּנָה; וְיִזָּהֵר מִלְּהַזְכִּיר שֵׁם שָׁמַיִם לְבַטָּלָה, שֶׁבְּכָל מָקוֹם שֶׁהַזְכָּרַת הַשֵּׁם מְצוּיָה, מִיתָה מְצוּיָה; וְיִזָּהֵר מִלִּשָּׁבַע, אֲפִלּוּ בֶּאֱמֶת, שֶׁאֶלֶף עֲיָרוֹת הָיוּ לְיַנַּאי הַמֶּלֶךְ וְכֻלָּם נֶחְרְבוּ בִּשְׁבִיל שֶׁהָיוּ נִשְׁבָּעִים שְׁבוּעוֹת אַף עַל פִּי שֶׁהָיוּ מְקַיְּמִים אוֹתָם; וְיִזָּהֵר מִלְּהִשְׁתַּתֵּף עִם עַכּוּ"ם, שֶׁמָּא יִתְחַיֵּב לוֹ שְׁבוּעָה וְעוֹבֵר מִשּׁוּם לֹא יִשָּׁמַע עַל פִּיךָ (שְׁמוֹת כג, יג). הַגָּה: וְיֵשׁ מְקִלִּין בַּעֲשִׂיַּת שֻׁתָּפוּת עִם הַעַכּוּ"ם בַּזְּמַן הַזֶּה, מִשּׁוּם שֶׁאֵין הַעַכּוּ"ם בַּזְּמַן הַזֶּה נִשְׁבָּעִים בַּעֲבוֹדַת אֱלִילִים, וְאַף עַל גַּב דְּמַזְכִּירִין הָעֲבוֹדָה זָרָה, מִכָּל מָקוֹם כַּוָּנָתָם לְעוֹשֶׂה שָׁמַיִם וָאָרֶץ אֶלָּא שֶׁמְּשַׁתְּפִים שֵׁם שָׁמַיִם וְדָבָר אַחֵר, וְלֹא מָצִינוּ שֶׁיֵּשׁ בָּזֶה מִשּׁוּם: וְלִפְנֵי עִוֵּר לֹא תִתֵּן מִכְשֹׁל (וַיִּקְרָא יט, יד) דַּהֲרֵי אֵינָם מֻזְהָרִין עַל הַשִּׁתּוּף (רַ"ן ספ"ק דַּעֲבוֹדָה זָרָה וְר' יְרוּחָם ני"ז ח"ה וְתוס' רֵישׁ פ"ק דִּבְכוֹרוֹת); וְלָשֵׂאת וְלָתֵת עִמָּהֶם בְּלֹא שֻׁתָּפוּת, לְכֻלֵּי עָלְמָא שָׁרֵי בְּלֹא יוֹם חַגֵּיהֶם (הַגָּהוֹת מַיְמוֹנִי פ"ח מֵהִלְכוֹת עֲבוֹדָה זָרָה) וְעַיֵּן בְּיוֹרֵה דֵּעָה מֵהִלְכוֹת ע"א סי' קמ"ז.

The Arrangement of Buying and Selling (ie. How One Should Conduct Themselves in Business). Containing 1 Se'if: Afterwards he should go to his work because any Torah that does not have work with it will end up becoming null and will cause sin because the poverty will remove from him knowledge of his Creator. Nevertheless, he should not make his work primary, but rather temporary, and his Torah permanent; and [through this] both will be sustained. He should do business honestly and be careful not to mention the name of Heaven in vain, because in every place where the mention of God's name [in vain] is found, death is found. And he should be careful not to take an oath, even in truth, because 1,000 cities belonged to King Yannai and all of them were destroyed because they took oaths, even though they kept them. And he should be careful from partnering with the gentiles, for perhaps [the gentile] will be obligated to take an oath and [the Jew] will violate [the transgression of] "[The names of other gods] should not be heard on your lips." Rem"a: And some are lenient with partnering with gentiles these days because the gentiles nowadays do not take an oath by idols. And even though they mention their foreign god, nevertheless their intention is to the Creator of heaven and earth, except that they associate the name of Heaven with other forces. And we do not find that there is in this [a violation by the Jew of] "Before a blind person you shall not place a stumbling block," because the gentiles are not warned regarding partnership [of God with other forces]. (Ra"n - the end of the first chapter of Avodah Zarah; Rabbeinu Yerucham - netiv 17, chelek 5; Tosafot - beginning of the first chapter of Bechorot). And to do business with them without partnering, all agree is permitted, except on the day of their festivals. (Hagahot Maimoni - first chapter of the Laws of Idol Worship). And see Yoreh Deah on the Laws of Idol Worship chapter 147.)