Must one nullify (bittul) chametz immediately after the nighttime search, and what is the reason?
Synopsis
All authorities agree that one must nullify chametz immediately after the nighttime search. The nighttime bittul covers only chametz one has not seen and not removed. The reason is that if any chametz remains unfound, the bittul prevents violation of bal yeira'eh. The authorities debate the underlying mechanism: is bittul required by Torah law (Rashi) or is it a rabbinic enactment as a safeguard (Ran, Tosafot)?
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