Jewish Symbols: Mezuzah

On the doorposts of traditional Jewish homes (and many not-so-traditional homes!), you will find a small case. This case is commonly known as a mezuzah (Heb.: doorpost), because it is placed upon the doorposts of the house. The mezuzah is not, as some suppose, a good-luck charm, nor does it have any connection with the lamb's blood placed on the doorposts in Egypt. Rather, it is a constant reminder of God's presence and God's mitzvot.
 
The mitzvah to place mezuzot on the doorposts of Jewish houses is derived from Deut. 6:4-9, a passage commonly known as the Shema (Hear, from the first word of the passage). In that passage, God commands the Jews to keep His words constantly in their minds and in their hearts, by (among other things) writing them on the doorposts of their house. The words of the Shema are written on a tiny scroll of parchment, along with the words of a companion passage, Deut. 11:13-21. On the back of the scroll, a name of God is written. The scroll is then rolled up placed in the case, so that the first letter of the Name (the letter Shin) is visible (or, more commonly, the letter Shin is written on the outside of the case).

The scroll must be handwritten in a special style of writing and must be placed in the case to fulfill the mitzvah. 

The case and scroll are then nailed or affixed to the right side doorpost on an angle, with a small ceremony called Chanukkat Ha-Beit (dedication of the house - yes, this is the same word as Chanukkah, the holiday celebrating the rededication of the Temple after the Maccabean revolt against Greece). A brief blessing is recited. 

Every time one passes through a door with a mezuzah on it, touch the mezuzah and then kiss the fingers that touched it, expressing love and respect for God and his mitzvot and reminding oneself of the mitzvot contained within them.