4th of Tebet, 5770
Most people think that the Mezuzah cover is really the Mezuzah and the inside, just a parchment. Well, actually, the inside IS the Mezuzah and the outside is just a decorative/protective case also known as: BAYIT, or “house of the Mezuzah”.
If you really want to know what’s “inside a Mezuzah”, you’re actually asking: what is written in the Mezuzah?
The Mezuzah then, is a small handwritten scroll which contains the first two paragraphs of the Shema Israel.
Why it contains exclusively these two paragraphs? Because in both of them appears the Mitzvah of Mezuzah ukhtabatam al mezuzot betekha ubisharekha.
Similar to the Tefilin which contains 4 paragraphs (two of the Shema and two of Kadesh li) because in those 4 paragraphs the Mitzvah of Tefilin is mentioned.
Going back to the Mezuzah, the Shema Israel contains the basic principles of our faith, and by placing the Mezuza in our entrance doors we are asserting and remembering our beliefs every time we come in and go out.
For more Information watch this 30 seconds video: “Inside” a Mezuzah? http://www.youtube.com/watch?v=PACu3aosp1g