Halakhah su Salmi 34:8

One must be very diligent to observe the commandment of mezuzah because it is the obligation of everyone at all times. Wherever you enter or leave your home, you will encounter the Oneness of Hashem, the Name of the Holy One, blessed is He, and recalling His love you will awaken from your lethargy and cease going astray after the vanities of the times. You will then realize that nothing endures forever except the knowledge of the Eternal One, and will immediately return to your senses, and walk in the path of the righteous. Our Sages of blessed memory say:¹²See Menachos 43b. "He who has tefillin on his head and on his arm, and wears tzitzis on his garment, and has a mezuzah on his doorpost, is sure not to sin, because he has many reminders and these are the guardian angels who save him from sin." And it is said: "The angel of Hashem encamps around those who fear Him and sets them free."¹³Psalms 34:8. Our Sages of blessed memory also say:¹⁴Maseches Shabbos 32b. "Because of the sin of mezuzah¹⁵I.e., the failure to observe the commandment of mezuzah. his sons and daughters may die young, whereas one who is diligent to observe the mitzvah of mezuzah will have his days lengthened," as it is said: "In order that your days be lengthened and the days of your children." ¹⁶Deuteronomy 11:21.