This minhag is an old one. It was mentioned (and rejected) by the Ra’avad[2] over 800 years ago as a safeguard that the beracha on bedikat chametz should not turn out to be l’vatala[3] if no chametz is found. This concern seems to assume that the beracha is recited over the finding of chametz.
Note that the beracha’s text is “al bi’ur chametz” (usually translated as “on the destruction of chametz”). This is a surprising phrase to use considering that the beracha is made before the bedika, rather than immediately prior to the burning, which is done only the following day.
There are at least four explanations as to the purpose of the beracha: 1) It refers primarily to the next day’s bi’ur but is recited before this important preparation for it.[4] 2) The beracha is primarily on the mitzva (perhaps Rabbinic) to search for chametz.[5] 3) The beracha includes the bitul chametz[6] performed after the bedika.[7] 4) The beracha is primarily on the removal of the chametz from one’s mind, which one does before the bedika commences.[8] The possibility of a problem of beracha l’vatala if no chametz is found (but known chametz will be disposed of tomorrow) arises only according to the second approach, and only if one further assumes that the search must turn up some chametz. Nonetheless, it is reasonable for a minhag to deal with a possible problem even if the concern is based only on a minority opinion, and this is the simple reading of the Rama,[9] who records the practice to put out bread before the bedika.
Some Acharonim reject the rationale and the practice of this minhag. The Taz[10] says that not only is it unnecessary to put out pieces of bread, but it is even detrimental, because one might not find everything that was put out. This concern is mitigated by the usual care exercised by whoever puts the pieces out to know the number (traditionally, ten) and location of the pieces. And after all, even irrespective of this minhag, it is always possible that chametz will be missed, and after doing a responsible bedika and bitul, one is not culpable for chametz that inadvertently remains.[11] Some suggest that one should put out pieces of specifically less than a k’zayit, so that if he misses one, it will not be large enough to cause him to violate the prohibition of possessing chametz.[12] Incidentally, there is an interesting machloket regarding whether people will take bedikat chametz more or less seriously due to the presence of the ten pieces; this may depend on where the pieces are placed.[13]
Other reasons are given for putting out the pieces of bread. The Mahari Weil[14] cites the gemara’s[15] insistence that bitul be performed at the time of bedika because we are concerned that one might otherwise forget to do the bitul. The Mahari Weil then argues that this association works well only if one actually finds some chametz; when he puts away the chametz that he found during bedikat chametz, he will remember to do bitul at that point. There are also Kabbalistic reasons, attributed to the Arizal, for the minhag.[16]
Another factor makes the minhag particularly appropriate in our times. In years past, people had much smaller houses and less property, and bedikat chametz was the main Pesach cleaning. Nowadays, in contrast, people spend weeks cleaning seriously in a manner that makes the bedika (almost) a formality, in which they do not actually look for real chametz.[17] Without the pieces of bread, then, the bedika is not a fully obligatory search, and the beracha is more problematic.[18]
Although there have been, over the centuries, poskim[19] who thought that this minhag is superfluous or detrimental, one should practice it unless he has specific reason not to.[20] An ancient minhag that is still in practice by the overwhelming majority of religious Jews deserves the appellation “the minhag of Israel is Torah,” all the more so when the logic behind it is readily understandable, even if debatable.