Position of the Mezuza
Question
Why do some people place the Mezuza standing up and some people place it diagonally?
Answer
Shalom!
Thank you for your question.
The position of the mezuza is one of the most interesting discussions of practical halacha, particularly due to the teaching I will share with you at the end.
The source for the dispute on the correct position of the mezuza is based on the Talmud (Menachot 33a) where it says that if one places his mezuza like a “sideways bolt”, the mezuza is invalid – no mitzva is performed.
Based on this, Rashi, the famous commentator says that mezuza must be placed vertically. He rules that a mezuza placed horizontally is invalid. On the other hand, Rabbeinu Tam, (his view is cited in the Tosfot commentary) rules that sacred items, such as holy scrolls (including a mezuza) and even a human corpse, must be placed horizontally. Rabbeinu Tam extends this to the parchments of the Tefillin ruling that the parchments must like horizontally unlike the universal custom today to place the parchments vertically, namely, “standing.” Indeed, even those who wear “Rabbeinu Tam Tefillin” do not follow the view of Rabbeinu Tam to place the parchments horizontally.
Regarding mezuza, the Shulchan Aruch (Y.D. 289:6) rules like the view of Rashi that a mezuza should be fastened vertically to the doorpost. However, the universal Ashkenazi custom is to place the mezuza diagonally which is meant to recall the opinion of Rabbeinu Tam.
As mentioned, there is a famous teaching that the slanted mezuza, seemingly compromising between the views of Rashi and Rabbeinu Tam teach us that in every Jewish home a spirit of compromise must prevail!