On Passover we eat matza, and this contains the secret of strengthened faith. Once a person’s faith has been strengthened by eating matza, he is able to eat anything without it doing him any harm. For one week (or eight days outside the Land of Israel), we refrain from eating hametz, and it is a period of spiritual cleansing and healing for the soul.

Eating matza reminds us of the secret of faith in God:

It is a mitzva to eat matza on Passover because it is a reminder, for all future generations, of the secret of faith. The Sages explained this: At the time of the exodus, the Jewish people also relinquished other errors [that is, idol worship] and obtained the secret of faith, and the Sages have explained this secret in numerous places.

If hametz is seen in such a negative light, why, in the Temple, do the priests bring the offering of the two loaves, which are hametz, on the festival of Shavuot? This is likened to the case of a prince who was very sick and required medicine.

We must consider the fact that on Passover, the Jewish people relinquished the bread that is called hametz…and now [on Shavuot], when they have merited to receive a much loftier bread [that is, the Torah, which is bread for the soul], is it not proper that all hametz be nullified and out of sight like on Passover? Why do we have this offering of hametz? This is comparable to a king who had one son who became sick. One day, the son desired to eat. It was said: The king’s son must eat a specific medicinal food, and until he has done so, there are to be no other foods found in the palace. This was carried out. Once his son had swallowed the remedy, the king said: From now on, he may eat whatever he desires, for it cannot harm him.

The king’s son represents the Jewish people, who were in need of healing when they left Egypt.

When the Jewish people left Egypt, they did not know the basis of the secret of faith. The Holy One, blessed be He, said: Israel must taste this remedy, and until they do so, they must not have another food. Once they had eaten the matza, which was the means to ascend and to understand the secret of faith, the Holy One, blessed be He, said: From this point forward, they may eat hametz, as it cannot harm them. (Zohar 2:41a, 183b)