יורה דעה קמ״חYoreh De'ah 148

Se’if 1א׳

שְׁלשָׁה יָמִים לִפְנֵי חַגָּם שֶׁל גּוֹיִים עוֹבְדֵי אֱלִילִים אָסוּר לִקַּח מֵהֶם וְלִמְכֹּר לָהֶם דָּבָר הַמִּתְקַיֵּם. וּמֻתָּר לִמְכֹּר לָהֶם דָּבָר שֶׁאֵינוֹ מִתְקַיֵּם עַד יוֹם חַגָּם, כְּגוֹן יְרָקוֹת וְתַבְשִׁיל. וְכֵן אָסוּר לְהַשְׁאִיל וְלִשְׁאֹל וּלְהַלְווֹתָן בְּלא רִבִּית (טוּר וְהַפּוֹסְקִים), וְלִלְווֹת מֵהֶם וּלְפָרְעָן, וְלִפָּרַע מֵהֶם מִלְוֶה בִּשְׁטָר אוֹ עַל הַמַּשְׁכּוֹן, אֲבָל מִלְוֶה עַל פֶּה נִפְרָעִים מֵהֶם מִפְּנֵי שֶׁהוּא כְּמַצִּיל מִיָּדָם, וּבִזְמַן דְּיָדָם תַּקִּיפָה, אֲפִלּוּ בִּשְׁטָר חָשִׁיב כְּמַצִּיל מִיָּדָם. וְאִם הִיא מִלְוֶה בְּרִבִּית, אֲפִלּוּ בְּמַשְׁכּוֹן חָשִׁיב כְּמַצִּיל מִיָּדָם.

For three days before the festival of gentiles who are idol-worshippers it is forbidden to buy from them and to sell to them a thing that lasts. And it is permitted to sell them a thing that does not last until the day of their festival, such as vegetables and cooked food. And likewise it is forbidden to lend an article to them and to borrow one from them, and to lend them money without interest (Tur and the poskim), and to borrow from them and to repay them, and to exact payment from them of a loan by deed or upon a pledge; but a loan by word of mouth — payment is exacted from them, because he is as one who saves from their hand. And in a time when their hand is strong, even by deed he is accounted as one who saves from their hand. And if it is a loan at interest, even upon a pledge he is accounted as one who saves from their hand.

Se’if 2ב׳

עָבַר וְנָשָׂא וְנָתַן בְּיוֹם חַגָּם, אָסוּר בַּהֲנָאָה. וְאִם נָשָׂא וְנָתַן בִּשְׁלֹשָׁה יָמִים שֶׁלִּפְנֵי הֶחָג, מֻתָּר בַּהֲנָאָה.

If he transgressed and did business on the day of their festival, it is forbidden in benefit. And if he did business in the three days before the festival, it is permitted in benefit.

Se’if 3ג׳

אִם הָיָה חַגָּם שֶׁל אוֹתָם הָעוֹבְדֵי כּוֹכָבִים יָמִים הַרְבֵּה, ג' אוֹ ד' אוֹ י', כָּל אוֹתָם הַיָּמִים כְּיוֹם אֶחָד הֵם, וְכָל אוֹתָם הַיָּמִים אֲסוּרִים עִם ג' לִפְנֵיהֶם.

If the festival of those idolaters (oved kokhavim — the standing term for a gentile) was many days — three, or four, or ten — all those days are as one day, and all those days are forbidden together with the three before them.