You are standing in front of the kosher l’Pesach shelves looking for a stamp of approval on the soda bottle. Your friend is frowning at the cap on the seltzer bottle. Your son, who is back from yeshiva in Israel, refuses to take home table salt without kosher l’Pesach stamp and somebody told you paper plates have starch. Short of hiring an escort mashgiach, what do you do?
A few background principles regarding the prohibitions of chametz mixtures on Pesach may provide some shopping guidance.
During the rest of the year, when forbidden food gets mixed up with permitted food, the mixture may be eaten if the ratio of the permitted food to the forbidden food is a certain prescribed amount and certain other conditions are met. Thus, if a piece of cold non‑kosher meat got mixed up with two cold pieces of kosher meat, all three pieces may be eaten.
This permission is based on the halachic principal of bitul berov, the majority nullifies the minority. Accordingly, it may be presumed that each piece of meat consumed belonged to the kosher majority. If the non‑kosher piece of meat was cooked in a pot containing kosher meat, and the ratio of the kosher meat to the non‑kosher meat was 60:1, batel beshishim, the whole mixture, including the non‑kosher meat, may be eaten.
These ratios do not, however, apply to chametz on Pesach. If chametz becomes mixed with non-chametz on Pesach, the mixture is prohibited even if the ratio of the permitted non‑chametz to the forbidden chametz is 1,000 to 1. This applies both to foods that blend together, lach belach, such as chametz flour and Pesach flour, and foods that do not blend together, yavesh beyanesh, such as a piece of kosher l’Pesach matzah with a piece of non-kosher l’Pesach matzah.
According to Rashi, the reason for this stringency on Pesach as opposed to the rest of the year is twofold.
First, the punishment for eating chametz on Pesach is karet, premature death at the Hand of God. Second, since the prohibition of chametz exists for only seven days a year, one might come to forget about it, lo bedilay minay. The combination of the severity of the punishment and the ease with which the prohibition may be forgotten require that the smallest amount of chametz, chametz memashehu, be prohibited.
According to the Rambam, the reason for the stringency on Pesach is that the chametz prohibition is a temporary prohibition, davar she’yesh lo matirin, because it lasts for only seven days. So why eat even the minutest amount of chametz on Pesach when one can wait until after Pesach and eat it without any concern?
A temporary prohibition cannot be nullified, irrespective of how high the ratio of the permitted food is to the forbidden food. A practical difference between Rashi’s explanation and the Rambam’s explanation is the case of chametz nuksha, spoiled or decomposed chametz. Although prohibited on Pesach, chametz nuksha does not incur the punishment of karet. According to Rashi, therefore, it could be batel b’shishim but according to Rambam it could not.
Certain combinations of chametz and non-chametz mixed together before Pesach could, however, become batel beshishim. For example, according to most opinions, beer mixed with wine before Pesach, or Pesach flour mixed with chametz flour before Pesach, which are both cases of mixtures that blend together, lach belach, can be batel b’shishim on Pesach. However, solids, which do not blend together, cannot be batel b’shishim on Pesach even if they were mixed before Pesach. The reason is that in the case of solids, which remain visibly identifiable on Pesach, the prohibition of chametz in the smallest amount, chametz bemashehu, is revived, chozer veniur, on Pesach. In the case of liquids or foods that blend together, the chametz part is neither visible nor identifiable in the mixture and therefore the prohibition of the smallest amount of chametz is not revived on Pesach.