The Very Short Answer
Chametz is any food product made from wheat, barley, rye, oats or spelt that has come into contact with water and been allowed to ferment and “rise.”
In practice, just about anything made from these grains—other than Passover matzah, which is carefully controlled to avoid leavening—is to be considered chametz. This includes flour (even before it is mixed with water), cake, cookies, pasta, breads, and items that have chametz as an ingredient, like malt.
The Biblical Basis
Just before the nation of of Israel left Egypt, G‑d commanded them to sacrifice the paschal lamb and then eat it with unleavened matzah and bitter herbs. G‑d then told them that they should replicate this feast every year on the anniversary of the Exodus: “It shall be for you a remembrance . . . seven days you shall eat matzah, and on the first day you should remove all se’or (sourdough, a leavening agent) from your homes. Anyone who eats chametz (leaven) from the first day to the seventh day shall be cut off from Israel.”
When Is It Forbidden?
According to Jewish law, it is forbidden to eat chametz after the fourth halachic hour on the morning before Passover. It is forbidden to derive any benefit from chametz at the fifth hour, and all chametz should be burned before the sixth hour. From then until after Passover, chametz is completely forbidden.
Why does the prohibition start before Passover begins?
The Torah states: “You shall slaughter the Passover sacrifice to the L‑rd, your G‑d. . . . You shall not eat leaven with it.” Tradition interprets this to mean that the prohibition of chametz starts from the time when the Passover sacrifice could be offered: from midday of the 14th of Nissan.
To prevent people from transgressing the prohibition inadvertently, the sages decreed that the prohibition of eating chametz starts two hours before midday, and the prohibition of deriving any benefit starts one hour prior to midday.
To see the relevant halachic times for your area, click here.
Getting Rid of Chametz
Long before Passover begins, we clean our homes, offices, and any other place that belongs to us to rid our homes of chametz. Although it’s praiseworthy to be stringent on Passover, keep in mind that dust isn’t chametz. The main purpose of cleaning and searching for chametz is to remove any chametz that one may come to inadvertently eat or derive benefit from during Passover. This obligation of getting rid of chametz does not extend to inedible chametz or tiny crumbs or particles of chametz that are soiled or spoiled. So the key areas to focus on are things that may come in contact with food, since we are forbidden to eat anything with even a trace of chametz.
The kitchen should be thoroughly cleaned, and all surfaces should be covered or koshered. Additionally, if you’re using your regular utensils or appliances for Passover, they will need to be koshered. If finances permit, it is better (and easier) to simply buy a set of Passover utensils. For more on the specifics of getting rid of chametz and koshering your kitchen, click here.
Some non-food items, such as vitamins and cosmetics, may contain chametz and will need to be disposed of or sold (see below). Please consult with a rabbi for a list of permissible and prohibited items.
On the eve of the 14th of Nissan, with just 24 hours to go to the Seder, we search our property—including home, office and car—for any chametz that may have been missed in the cleaning process.
The custom is to conduct the search using a candle, feather, wooden spoon and a (paper) bag for collecting any chametz found. Have someone place 10 pieces of bread throughout the house to be found during the search.
Before we start the search, we recite the blessing (found here). No interruption should be made between reciting the blessing and the start of the search. Additionally, during the search, we only discuss that which pertains to the search for chametz.
In order to ensure that we remember to conduct the search on time, it is forbidden to eat or even learn Torah after nightfall until after the search has been completed.
Following the search for chametz, we recite a “nullification statement” renouncing all ownership of any chametz that, unbeknownst to us, may still be in our possession. The nullification statement should be said in a language that you understand, and can be found here.
Through nullifying our chametz, we consider it as no more than dust and thus ownerless, thereby fulfilling the mitzvah of removing chametz from our possession.
Utensils used for chametz (and chametz itself that you are reluctant to dispose of) may be sold to a person who is not Jewish for the duration of Passover. (Some have the custom not to sell any real chametz, although this is not the Chabad custom.)
The sold chametz and utensils should be set aside in a designated place (e.g., closet or cabinet), which is rented to the non-Jewish buyer until after Passover. This storage place should be clearly marked, so no one can take anything from there through force of habit.
The sale of chametz to the non-Jew is not a symbolic sale, but a legally binding transaction, and must therefore be conducted by a competent rabbi.
After writing a bill of sale, one may leave the chametz in his home without transgressing the prohibitions of not seeing or having chametz, since the chametz no longer belongs to him.
For more about the sale of chametz, click here.
To arrange for the sale of your chametz, click here.
On the 14th of Nissan, before the sixth hour of the day, we burn any chametz that we still have. This includes the bag of chametz from our search the previous night.
After the chametz is burned, we again recite a nullification statement. However, this nullification statement has a slightly different wording than what was said at night after the search for chametz. The statement recited at night includes only chametz that was missed in the search, but doesn’t include chametz set aside to be sold or eaten in the morning. When we burn the chametz, the statement includes all chametz that may still be in our possession, and serves as a final “safety measure” for a chametz-less Passover.
The text can be found here.
Due to the gravity of the prohibition of chametz, the medieval Ashkenazic rabbis also forbade the consumption of any kitniyot (very loosely translated as “legumes”) on Passover, since they can be confused with the forbidden grains. This includes (but is not limited to): rice, corn, soybeans, stringbeans, peas, lentils, mustard, sesame and poppy seeds. This ban was accepted as binding law by Ashkenazic Jewry.
The prohibition extends only to the consumption of kitniyot; there is no obligation to destroy or sell kitniyot products before Passover, and we can derive benefit from kitniyot products (e.g., pet food) during Passover.
For more on kitniyot, click here.
Chametz After Passover
Due to the severity of the prohibition of owning chametz on Passover, the rabbis of the Talmud established an after-the-fact penalty for owning any chametz products during Pesach. This prohibition is known as chametz she’avar alav haPesach. One may not consume or even derive benefit from such chametz, and if chametz is found either on or after Passover that was owned by a Jew during Passover, it needs to be destroyed.
So, what does that mean on a practical level? When you’re purchasing chametz products after Passover from a Jewish-owned store, the owner cannot have owned that chametz during Passover. If he did, you’ll need to refrain from purchasing any chametz products there until it is deemed that a sufficient amount of time has passed for all of those chametz products to have been sold. Consult your local rabbi with any questions regarding stores in your area.
This prohibition does not apply to kitniyot, since one is permitted to own it on Passover.
On a Spiritual Note
Chametz and matzah are almost the same substance, containing the same ingredients of flour and water. The one key difference is that while chametz bread rises, filling itself with hot air, the matzah stays flat and humble.
Thus, chametz represents that swelling of ego that enslaves the soul more than any external prison. It is for this reason that once a year on Passover, when we celebrate our freedom from slavery and our birth as a nation unto G‑d, we are extremely careful to eradicate any chametz that we may have.
The flat, unpretentious matzah represents the humility, self-effacement and commitment that are the ultimate liberators, enabling us to connect to G‑d without our egos getting in the way. And that is why eating matzah on Passover is so fundamental to our faith.