Menachot 33: Does the Mezuza Protect Us? How?

Some notes on today's daf:

• We learn from Rava that we must affix the mezuza on the doorpost facing the public domain
• if the doorpost is wide, the mezuza should be placed in the tefach, four fingerwithdth length, closest to the public/outside
• The rabbis argue that this is so that the mezuza can be reached easily when entering a home
• Rabbi Chanina of Sura argues that this allows the mezuza to protect the entire house
• Rashi suggests that the mezuza protects us from destructive forces
• The Gemara quotes Tehillim 121:5, where Rabbi Chanina suggested that G-d dwells outside of our homes, guarding us from the outside unlike a king whose servants live outside of his home
• proof texts include the blood left on the doorposts to protect the sons of Israelite slaves in Egypt before the exodus
• the mezuza mentions long life to us and our children, and it may have included the names of angels in the past
• of course some rabbis believe the that mitzvah should be done for its own sake and not for 'protection'
• The Rambam asserts that the mezuza should not be used as an amulet (Hilchot Tefillin 5:4)
• The Rambam adds that the 'protection' that the mezuza offers comes in the form of a reminder of G-d and thus it keeps us from sin