Landlord-tenant disputes are the bread and butter of many a lawyer. No law can account for any eventuality, and the inherent conflict of interest whenever money is involved makes such disputes commonplace.
"They asked of Rav Nachman bar Yitzchak: One who rents a house to a friend on the 14th [of Nissan]; upon whom is the obligation to check for chametz?" (Pesachim 4a). With the obligation to check for chametz beginning on the eve of the 14th, it seems reasonable to require the owner to check for chametz before handing over possession the next day. On the other hand, the purpose of bedikat chametz is to prevent one from violating the prohibition against owning chametz on Pesach[1], a prohibition that begins only in the mid-morning of the 14th of Nissan. By that time the tenant is in possession of the apartment so perhaps the obligation to check devolves upon him.
The Talmud raises and rejects, the notion of looking to the law regarding the obligation of a mezuzah in a rented home as a comparative model. In that case, all agree that "mezuzah chovat hadar", the one who lives in the home, i.e., the tenant, must put up the mezuzah[2]. Thus, if no one lives in a home, there is no need for a mezuzah on the door; however, one must rid each and every abode one owns of chametz--even if one has never lived there.
The Talmud then rules that it depends on the moment the keys were handed over. Whoever has the keys--and thus, possession--when the eve of the 14th arrives must do the bedikat chametz.
That is all nice, in theory. But what happens, the Gemara queries (Pesachim 4b), when one takes possession of a home just a few hours before Pesach--something quite common, with Pesach travels so popular today--and, lo and behold (and in violation of Jewish law), the place was not cleaned for Pesach? Being that the newly arrived guest must unexpectedly clean the apartment, perhaps he can void his rental contract, claiming a mekach taut, a transaction conducted under false pretenses.
Abaye's response is a most beautiful testament to the love we are meant to have for mitzvah opportunities. Not only in a place where people check homes themselves, but even if one must actually pay money to the "local bedikat chametz cleaners", the rental agreement stands. Abaye explains that this is "because it is pleasant for a person to perform a mitzvah with his money".
What makes this even more striking is the fact that bedikat chametz is not a mitzvah in itself, but rather is a means by which one avoids other potential prohibitions. But this is the love the Jew has--or should have--for mitzvoth in general, and Pesach in particular. While Jewish law is insistent that one not spend excessive amounts in the performance of mitzvoth, the few extra dollars to get the house fit for Pesach is something that should bring one joy.
Sadly, for many today, Pesach brings little joy--the dread of more cleaning for Pesach is such that we may find Abaye's analysis no longer true. That is most unfortunate. With the best of intentions, but most unfortunate unintended consequences, much of what passes for bedikat chametz today is no more than excessive spring cleaning[3]. Unless there is a good chance of finding edible chametz, no checking is really needed. Often we get so caught up in fulfilling our obligations that we forget that mitzvoth are meant to be exciting, bringing us great joy. That is an area well worth being "strict" about.
[1] Such is the explanation of Rashi (Pesachim 2a). The Tosafists, however, disagree, noting that nullification, bitul chametz, absolves one of the prohibition of owning chametz. Rather, we check for chametz lest one mistakenly come to eat chametz on Pesach.
[2] This would seem to run against the well-known law that when one moves out of a home, one must leave the mezuzah for the incoming inhabitants (provided they are Jewish). That requirement apparently flows not from the laws of mezuzah, but from those of gemilut chasadim.
[3] The first Mishnah in Pesachim discusses a butler going down to a wine cellar, potentially with bread in hand. And yet, even the strict rejected view of Beit Shammai requires only a very small portion of the cellar be checked for chametz.
