QUESTION: I have noticed that the door frames of some Jewish homes have a small tubular case affixed at about eye level. I have heard this is some kind of Jewish religious object. What is it, and what is its purpose?

ANSWER: The small tube is called a mezuzah. Generally these are about the size of a man’s index finger, but they may be larger or smaller. They vary greatly in design, some being made of metal and others of wood or ceramic materials.

The mezuzah contains a small piece of parchment upon which a scribe has hand copied two Bible passages (Deut. 6:4-9 and 11:13-21). The passages begin with Hear, O Israel, the Lord our God, the Lord is one,” and end with “And thou shalt write them (meaning the laws of God) upon the doorposts of thy house and upon thy gates.” The reverse side of the parchment is inscribed with the word Shaddai, which is usually visible through a small opening, although sometimes it is embossed or written on the outer casing itself. Shaddai is one of the Old Testament appellations for God, meaning “Almighty.” Some have conjectured that the three Hebrew characters of the word Shaddai represent the initial letters of the phrase Shomer Delasot Yisrael, which means “Guardian of the homes (literally doors) of Israel.”

There are strict rabbinic regulations for affixing the mezuzah. It must be attached to every door of a Jewish house except the bathroom. It must be nailed on, not hung, and must be positioned diagonally unless the doorpost is too narrow. Its placement must be within the upper third of the doorpost, and on the right-hand side as one enters.

The affixing ceremony, which is somewhat akin to a house dedication, is accompanied by a special prayer.

“Barukh attah adonai, elohenu melekh haolam, asher kidshanu bemitzvotav, vetzivanu likboa mezuzah.”

“Praised be Thou, O Lord our God, King of the universe, who hast sanctified us by Thy commandments, and hast commanded us to affix the mezuzah.”

Orthodox Jews usually kiss the mezuzah upon entering and leaving the house as a reminder that they must fear God both within their homes and in the outside world.

Some ultra-Orthodox Jews treat the mezuzah as an amulet, with almost magical powers. One Hassidic rabbi claimed to have “scientific knowledge” that homes where there were mezuzahs affixed had less fires and catastrophes than those without a mezuzah. However, for the most part, the presence of a mezuzah merely indicates a Jewish home and is intended to witness to the fact that its residents believe in the God of Israel.