The Ritual Mysticism and Magic of Passover
[the four sons, as envisioned by Arthur Syzk]
The word pesach, normally translated as “passover,” more properly simply means “protection,” in the sense of apotropaic/spiritual protection (the Assyrian cognate verb means to "placate [a spirit]"). The blood of the first paschal animal (a lamb or goat) offering served as talismanic ritual against death entering the home.
In both pietist and kabbalistic traditions of Judaism, all of the elements of the Passover are thought to have spiritual-theurgic power. The burning of all leaven on the eve of Passover, for example, is meant to symbolize the destruction of the Yetzer ha-Ra in one’s self, a task which, like removing all leaven, can never be perfectly achieved (J. Ber. 4:2, 7d).
Central to the holiday is unleavened Bread: (matzah). A large, cracker-like wafer that is eaten throughout the holiday of Passover in place of risen bread. It is eaten to commemorate both the slavery and liberation our ancestors experienced. It is therefore a symbol of paradox: it simultaneously symbolizes slavery and freedom. Matzah is made using only specially supervised (keeping it free from exposure to airborne yeast) wheat and water (the essential nutrients for life). It is then baked no more than eighteen minutes (the number symbolizing life).
It is a symbol of ritual and spiritual purity; Jews eat matzah free of leaven just as we must free ourselves of the “leaven” of ego, sin, and old habits. At the Seder, three pieces of matzah are prominently displayed, reminding Jews of both the three Biblical classes of Jews (Priest, Levite and Israelite) and of the three epochs (the Garden of Eden, historic time, and the time of the Messiah).
One aspect of unleavened bread that has particular occult symbolism is the afikoman. The afikoman is one-half of a matzah wafer that is publicly broken, only to be hidden away during the Seder. Children must then find it or steal it from the holder in order for the Seder to continue. Originally intended as a pedagogical tool to keep the attention of children during the ceremony, by the Middle Ages the afikoman became a object of life-giving power and started to be used as an amulet against the evil eye. Customs include preserving a piece at home for good luck, while some may actually carry crumbs of the afikoman in their coat pockets. Pregnant women can keep a piece of afikoman nearby to ensure an easy labor. According to one tradition, an afikoman kept seven years can avert a flood or other natural disaster..
Much of the Seder ritual is constructed around groupings of fours: four questions, four types of sons [Jews], and four cups of wine. While the choice of the number four seems at first to simply be a means of distinguishing the holiday, perhaps a mnemonic device for remembering the steps of the Seder at a time before printed material was widely available, over time there are a number of theurgic and magical customs that have become associated with the holiday and the apparatus of its observance. The most famous of these is the medieval incantation of protection invoked at the holiday known as the "Sixteen-Edged Sword of the Almighty," which is also a multiple of four. It involved removing sixteen (a different ritual from the ten we know to today) drops from a wine glass during the seder recitation of the plagues to prevent dever, pestilence (which is mentioned 16 times in the book of Jeremiah) from having it sway over the family and community in the year ahead. 
Zal G'mor: To learn more, consult the Encyclopedia of Jewish Myth, Magic, and Mysticism: http://www.amazon.com/Encyclopedia-Jewish-Myth-Magic-Mysticism/dp/0738709050
1. Trachtenberg, 1939, pp. 134, 295.
2, Kanarfogel, 2000, pp. 137-38.