There are three distinct prohibitions that apply to hametz on Passover: it is prohibited to eat it, it is forbidden to derive benefit from it (e.g., by selling it or feeding it to animals), and it is prohibited to have it in one’s possession. Not only is actual hametz prohibited on Passover, but even a mixture that has hametz as one of its components is forbidden.

Hametz is a product made from one of the five kinds of grain (see further) that has come into contact with water and reached a certain level of fermentation called himutz, “leavening.” From a scientific perspective it is not easy to define this leavening, but there are clear and practical definitions of this category in halakha, some of which will be detailed below.

The five types of grain recognized by halakha are: wheat, barley, oats, spelt, and rye. If any of these grains becomes leavened, it is strictly prohibited during Passover. In practice, this includes most regular baked goods and pastry products, pasta, etc. The same applies to many beverages, especially beer and some liquors, such as vodka or whiskey, which are made from fermented grains.

The prohibition of hametz is more severe than the prohibitions against most forbidden foods, such as non-kosher meat or mixtures of meat and milk.

This expresses itself in several ways:

(1) Eating hametz on Passover, like eating on Yom Kippur, is punishable by karet, meaning excision, being “excised from Israel” (Exodus 12:15).

(2) Generally, if a small amount of forbidden food becomes mixed with more than sixty times its volume of kosher food, the non-kosher component is halakhically “nullified” and it is permitted to eat the entire mixture. By contrast, if there is any admixture of hametz at all in a food on Passover, even a minute amount, all the food is prohibited.

(3) During Passover, it is prohibited not only to consume hametz but also to derive benefit from it. One may not feed it to an animal, sell it, or even use it as fuel for a fire from which one derives benefit. Therefore, those who raise animals or have pets must feed them food on Passover that does not contain hametz.

(4) Hametz may not even be found in the possession of a Jew on Passover.

Due to the severity of the prohibition of hametz on Passover, it is appropriate to exercise great caution to ensure that one does not violate this prohibition. Even rabbis who do not tend toward stringency in their rulings all year are stricter regarding any question that involves hametz on Passover. It is important to know that apart from basic, unprocessed animal and vegetable products, such as meat, fish, eggs, fruits, and vegetables, there is nothing that may be eaten on Passover without a reliable “kosher for Passover” certification.

The prohibition against having hametz in one’s possession on Passover starts from the time of burning the hametz and lasts until the end of the last day of the holiday. This accounts for the frenzy of house cleaning as Passover approaches that has taken hold of Jews for generations.

One should calculate one’s shopping needs in the weeks before Passover, so that most of the hametz products that he buys will be consumed before the holiday and he will not have to dispose of them. If, nevertheless, some hametz remains in the house, it must be burned on the day before Passover or sold to a non-Jew, as detailed below in the halakhot of Passover eve.

Further reading: For more on the severe prohibition of hametz, see A Concise Guide to Mahshava, p. 95.

According to the halakha, even a small amount of hametz is prohibited to be in one’s possession on Passover. This is the basis for the requirement of thorough cleaning.

Even a cookie or a few pretzels that lie hidden between the upholstery and the backrest of an armchair in the living room causes one to violate the prohibition of “it may not be found” (Exodus 12:19). With that said, it is important to differentiate between the cleaning that is halakhically necessary, and activities undertaken by some, such as scrubbing walls and ceilings, which are entirely unnecessary from a halakhic perspective.

In general, the halakha requires one to inspect and clean only those places where there is a reasonable concern that hametz is located. This includes: all areas of the kitchen, pantry, and dining area, including chairs and cabinets; children’s rooms, as children are likely to bring food there; and any other part of the house where it is possible that hametz was brought during the year. Children’s toys should be checked, and if one wants them to be used on Passover they must be cleaned. It is recommended to put toys made of cloth or waterproof plastic inside a pillowcase and machine wash them gently. It is also necessary to thoroughly clean the family car.

By contrast, places such as clothing closets or bookcases, which do not generally contain food, do not have to be cleaned according to the halakha. Bear in mind that dust is not hametz.

Further reading: To read about the inner spiritual cleansing that can be inspired by the process of cleaning for hametz, see A Concise Guide to Mahshava, p. 96.

Spices that have possibly become mixed with hametz, such as flour, should be burned or sold to a non-Jew.

The prohibition on Passover against deriving benefit from hametz or from a mixture of hametz leads many people to be very stringent, even regarding items that are not edible. There are those who are careful on Passover to use only those cosmetics and hygiene products, body lotions, shampoos, and the like, that are stamped as kosher for Passover.

One should consult lists of kosher-for-Passover products that are publicized by kashrut organizations. In Israel, lists of medicines that are certified kosher for Passover are readily available at pharmacies and on the internet. Anyone who needs to take medicine orally on Passover should consult a rabbi, as in some cases it is permitted to take medicine on Passover even if it contains hametz ingredients. Even if a medication is not kosher for Passover, this does not mean that it must be destroyed before the holiday, as long as it is unfit for consumption by a dog (this is the halakhic criterion for defining “food” when it comes to hametz).

There are products whose main ingredients are not hametz, but they nevertheless contain small amounts of hametz. Due to the miniscule percent of hametz overall in the product, the manufacturer is not required by law to list the hametz ingredient on the packaging. Therefore, one should look for specific kosher-for-Passover certification, confirming that there is no hametz in the product at all. It is not sufficient to merely read the list of ingredients on a product package.

Moreover, there are certain products that are sometimes made from hametz and on other occasions are not. For example, alcohol in its various forms can be produced from a variety of grains, in which case it is hametz and thus prohibited on Passover. Alcohol can also be made from sources that are not hametz. Therefore, one cannot assume that all products of the same general type have the same status.

Regarding kosher food in general, and the permissibility of products for Passover in particular, one should not rely on the statements of sellers in stores or even on the phrase “Kosher for Passover” that appears on the package. To ascertain that a product is indeed kosher for Passover, one must look for the seal of a known, reliable organization that certifies the product to be kosher for Passover.