Write them on the doorposts of your house and upon your gates.
A person is obligated to put a mezuzah on the doorpost of almost every
room in his house and business. The mezuzah contains the two paragraphs
of “Shema” (Devarim 6:4–9) and “Vehayah” (ibid. 11:13–21).
When one passes a mezuzah, he should think of the text inscribed inside,
which teaches us to love Hashem. When he sits at his table, he can focus
on the mezuzah to remind himself to follow the Torah’s teachings. When
speaking on the phone, he may also utilize the mezuzah as a reminder to
guard his tongue. This is the purpose of a mezuzah (Awake, My Glory, p.
The Rambam teaches that the mezuzah should bring us to the realization
that nothing endures forever, besides the awareness of Hashem and His
service (Hilchos Mezuzah 6:13).
One who is careful with the mitzvah of mezuzah will merit to have a
beautiful home. (Shabbos 32b)
The Rambam (Hilchos Mezuzah 5:4) also discusses those who add words, such
as the names of angels or other verses of the Torah, inside their mezuzos.
By doing this they forfeit their portion of the World to Come, for not
only are they corrupting the mitzvah, but they are also taking a great
mitzvah of testifying to Hashem’s oneness and turning it into an amulet
for personal benefit.
The Kesef Mishnah explains that when we perform the mitzvah properly in
order to fulfill Hashem’s command, it also provides protection for the
house and many other benefits.