Siman 440
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א עַכּוּ"ם שֶׁהִפְקִיד חֲמֵצוֹ אֵצֶל יִשְׂרָאֵל, אִם הוּא חַיָּב בְּאַחֲרָיוּתוֹ מִגְּנֵבָה וַאֲבֵדָה, בֵּין שֶׁהוּא בְּבֵיתוֹ בֵּין שֶׁהוּא בְּכָל מָקוֹם בִּרְשׁוּתוֹ, חַיָּב לְבַעֲרוֹ. הַגָּה: וַאֲפִלּוּ חָזַר וְהִפְקִידוֹ בְּיַד עַכּוּ"ם אַחֵר (הַגָּהוֹת אַלְפָסִי פ"ק דִּפְסָחִים). וְיֵשׁ אוֹמְרִים שֶׁאֲפִלּוּ אֵינוֹ עָלָיו אֶלָּא שׁוֹמֵר חִנָּם שֶׁחַיָּב בִּפְשִׁיעָה, חַיָּב לְבַעֲרוֹ. וַאֲפִלּוּ אִם אֵינוֹ חַיָּב בְּאַחֲרָיוּתוֹ בַּדִּין, אֶלָּא שֶׁיּוֹדֵעַ שֶׁהָעַכּוּ"ם אַלָּם וְיִכְפֵּהוּ לְשַׁלֵּם אִם יֹאבַד, חַיָּב לְבַעֲרוֹ; וְיֵשׁ חוֹלְקִים.
1 The law of chametz belonging to a non-Jew deposited with a Jew — four סעיפים: A non-Jew who deposited his chametz with a Jew: if the Jew is responsible for it in cases of theft or loss—whether it is in his house or anywhere under his domain—he is obligated to remove it. Rema: even if he then re-deposited it with another non-Jew (Hagahot Alfasi, beginning of Pesachim). And there are those who say that even if he is only an unpaid guardian, who is liable only for negligence, he must remove it. And even if he is not legally liable, but he knows that the non-Jew is forceful and will compel him to pay if it is lost, he must remove it; and there are those who disagree.
ב וְאִם אֵינוֹ חַיָּב בְּאַחֲרָיוּתוֹ, אֵינוֹ חַיָּב לְבַעֲרוֹ אֲפִלּוּ אִם כָּבוּשׁ תַּחַת יָדוֹ, כְּגוֹן שֶׁהוּא גֵּר תּוֹשָׁב וְשָׁרוּי עִמּוֹ בֶּחָצֵר. וְצָרִיךְ לַעֲשׂוֹת לְפָנָיו מְחִצָּה גָּבוֹהַּ י' טְפָחִים, כְּדֵי שֶׁלֹּא יִשְׁכַּח וְיֹאכְלֶנּוּ. הַגָּה: וְעַכּוּ"ם שֶׁהִנִּיחַ חָמֵץ בְּבֵית יִשְׂרָאֵל בְּלֹא רְשׁוּתוֹ, כּוֹפֶה עָלָיו כְּלִי (ריב"ש סי' ת"א); וְדַוְקָא בְּיוֹם טוֹב, אֲבָל אִם הוּא קֹדֶם יוֹם טוֹב צָרִיךְ לַעֲשׂוֹת מְחִצָּה (עַיֵּן לְעֵיל סִימָן תמ"ו סָעִיף א').
2 If he is not responsible for it, he is not obligated to remove it—even if it is under his control, such as in the case of a resident convert living with him in the courtyard; however, he must make a partition ten handbreadths high so that he not forget and eat it. Rema: if a non-Jew placed chametz in a Jew’s house without permission, he covers it with a vessel (Rivash §401). This applies specifically on Yom Tov; but if it is before Yom Tov, he must make a partition (see above §446:1).
ג עַכּוּ"ם שֶׁנִּכְנַס לְבֵית יִשְׂרָאֵל וַחֲמֵצוֹ בְּיָדוֹ, אֵינוֹ זָקוּק לְהוֹצִיאוֹ אַף עַל פִּי שֶׁהַיִּשְׂרָאֵל רוֹאֶה חָמֵץ שֶׁל עַכּוּ"ם אֵין בְּכָךְ כְּלוּם. אֲבָל אָסוּר לְהַעֲלוֹתוֹ עִמּוֹ עַל הַשֻּׁלְחָן וַאֲפִלּוּ בְּהֶפְסֵק מַפָּה.
3 If a non-Jew enters a Jew’s house with his chametz in hand, the Jew is not required to remove him. Even though the Jew sees the chametz of a non-Jew, there is no issue; however, it is forbidden to have it brought onto the table with him, even with a separating cloth.
ד יִשְׂרָאֵל שֶׁהִפְקִיד חֲמֵצוֹ אֵצֶל יִשְׂרָאֵל חֲבֵרוֹ אוֹ אֵצֶל הָעַכּוּ"ם, אַף עַל פִּי שֶׁקִּבֵּל עָלָיו הַנִּפְקָד אַחֲרָיוּת, עוֹבֵר עָלָיו [אַף] הַמַּפְקִיד.
4 If a Jew deposited his chametz with another Jew or with a non-Jew, even if the guardian accepted responsibility, both the depositor and the guardian transgress regarding it.