אורח חיים תל״זOrach Chayim 437

Se’if 1א׳

הַמַּשְׂכִּיר בַּיִת לַחֲבֵרוֹ לְצֹרֶךְ י"ד וּמִמֶּנּוּ וָאֵילָךְ, וְקֹנֵהוּ בְּא' מֵהַדְּרָכִים שֶׁשְּׂכִירוּת קַרְקַע נִקְנֶה בּוֹ, אִם עַד שֶׁלֹּא מָסַר לוֹ הַמַּפְתֵּחַ חָל י"ד עַל הַמַּשְׂכִּיר לִבְדֹּק; וְאִם מִשֶּׁמָּסַר לוֹ הַמַּפְתֵּחַ חָל י"ד, עַל הַשּׂוֹכֵר לִבְדֹּק.

One Who Rents to His Fellow, Upon Whom Does the Obligation to Destroy Chametz Fall. Containg 4 paragraphs: When a person rents a house to a tenant before the onset of the night of the 14th of Nissan, and the tenant acquired [the rights to live in the house] through one of the processes through which the rental of a home is validated, if before he hands him the key, the responsibility falls on the landlord to inspect, and if the key is handed over to him, the responsibility falls on the tenant to inspect.

Se’if 2ב׳

הַשּׂוֹכֵר בַּיִת מֵחֲבֵירוֹ בְּי"ד וְאֵינוֹ יוֹדֵעַ אִם הוּא בָּדוּק, אִם הוּא בָּעִיר שׁוֹאֲלוֹ אִם בְּדָקוֹ; וְאִם אֵינוֹ בָּעִיר, חֶזְקָתוֹ בָּדוּק וּמְבַטְּלוֹ בְּלִבּוֹ וְדַיּוֹ.

If the tenant rents a house from his friend on the 14th of Nissan, and he does not know the landlord checked (for Chametz), if the landlord is in town, he asks if it has been inspected, and if he is not in town, his assumption is that it has been inspected, and he cancels it in his heart, and it is sufficient.

Se’if 3ג׳

הַמַּשְׂכִּיר בַּיִת לַחֲבֵרוֹ בְּחֶזְקַת בָּדוּק וְנִמְצָא שֶׁאֵינוֹ בָּדוּק, עַל הַשּׂוֹכֵר לִבְדֹּק וְאֵינוֹ מִקַּח טָעוּת; וַאֲפִלּוּ בְּמָקוֹם שֶׁבּוֹדְקִים בְּשָׂכָר, שֶׁהֲרֵי מִצְוָה הוּא עוֹשֶׂה. הַגָּה: וְיֵשׁ אוֹמְרִים דְּצָרִיךְ לְהַחֲזִיר לוֹ שְׂכַר הַבְּדִיקָה הוֹאִיל וְהִתְנָה בְּהֶדְיָא שֶׁיִּהְיֶה בָּדוּק. (הַמַּגִּיד פ"ב וּמַשְׁמָע לְעֵיל סי' י"ד).

The landlord rents a house to his friend with the presumption of it being inspected, and if it is found to be uninspected, it is the responsibility of the tenant to inspect, and the transaction cannot be retracted. This applies even in a place where it is customary to hire someone else to check, as it is a mitzvah to fulfill. Rema: Some say that the landlord must return the inspection fee to the tenant since it was explicitly stipulated that it would be inspected (HaMagid, Perek 2, and see above Siman 14).