There is a mitzvah to install kosher mezuzot on the doorposts of our homes. As we shall see, the question of when to put up the mezuzah depends on whether you are renting or buying the home, as well as whether the home is in Israel or in the diaspora.

Let's first start with the simpler scenario.

Purchasing a Home

When one buys a home, whether in Israel or the diaspora, one is required to install a mezuzah with a blessing1 right when one moves in (or, according to some, even when just one’s furniture is moved in if that is done some time earlier2 ).3

Renting a Home

When it comes to renting (or borrowing) a home, there is a difference whether one is renting inside Israel or in the diaspora.

Renting in the Diaspora: When renting in the diaspora, one is not obligated to install a mezuzah for the first 30 days that one lives there. This is because the Torah only requires you to install a mezuzah in a home that is “your dwelling.” If one is renting, the obligation is on the renter, not the owner. However, the "dwelling" space needs to be your regular living space (and not merely short-term accommodation), and if you do not own it, that is achieved after 30 days.4

Despite this generally accepted ruling, there are some who rule that if one wishes, one may affix a mezuzah and recite the blessing on a rental even before 30 days.5 (Additionally, some are of the opinion that if you have a lease contract that extends for more than 30 days, your obligation starts right away.6 )

In Practice: It is the custom of many, including Chabad,7 to install the mezuzot on a rental immediately upon moving in (without reciting the blessing). Then, after 30 days have passed, you remove the mezuzah from one doorway (which requires a mezuzah according to all opinions)8 and have that mezuzah checked, or (when possible) replaced with a better quality one.9 You recite the blessing of affixing the mezuzah when putting the mezuzah back up, having in mind the other mezuzot as well.10

Following this procedure allows you to have your cake and eat it too, as it provides the spiritual protection of mezuzot on all doors right away and allows you to make the blessing after 30 days.

Renting in Israel: Similar to when purchasing a home, a renter in Israel is obligated to affix the mezuzot right away (with a blessing).11 This was enacted to encourage Jewish people to live in Israel.12 How so?

The rationale13 was that having the mezuzot hung right away would discourage the new renter from second-guessing their move and moving out, since it is forbidden to take down mezuzot once they have been installed. In addition, if one does move out, the already-installed mezuzot would encourage another Jewish family to move in.

Another explanation is since one of the aspects of a mezuzah is that it protects the home. In Israel, in order to encourage Jewish people to live there, the mezuzah is put immediately so that there will not be a day without protection.14

Based on this halachah, the Rebbe15 emphasized the added importance of affixing kosher mezuzot in the Land of Israel. In addition to their bringing protection and peace to the inhabitants, this hastens the fulfillment of G‑d’s promise regarding the future Redemption: “And I will grant peace in the Land, and you will lie down with no one to frighten [you] . . . and no army will pass through your land.”16

May this promise be fulfilled with the coming of Moshiach speedily in our days!