Our sages explain that it is imperative for a person to both know and understand the reasons for the mitzvot, to the best of his or her abilities (see Miamonides’ Guide to the Perplexed 3:31). This would also include, it seems, the nature of the mitzva, and whether or not serves as a form of protection or confers some other benefit. Last week, an article in The Jerusalem Post claimed that the mezuza offers no protection.What follows is a discussion of the reasons for the mitzva of mezuza and the sources that indicate it does indeed offer protection.The Ramban (Rabbi Moshe ben Nahman), in his commentary to the Book of Exodus writes that with the proper observance of the mitzva of mezuza a person acknowledges five very important things, namely: God’s creation of the world; His omniscience; His Divine providence; belief in prophecy and the other fundamental principles of the Torah; and belief that the mercy of God is very great to those that do His will, since He brought us out of Egypt through the merit of our forefathers who delighted in fear of God’s Name.The reasons cited by the Ramban for the performance of this mitzva were well-known throughout Jewish history. For example, even Josephus writes (Antiquities IV 8:13) that the mezuza is placed upon the door post “in order that His Benevolent Providence may be known everywhere.”According to Sefer HaChinuch (Mitzva 423), the reason for the mitzva of mezuza is so that we should have a constant reminder of our Creator, whenever we enter or exit our homes, or even the individual rooms within our homes.The Ravad (Rabbi Abraham ben David) explains that the mezuza is one of the Divine aids that God gave us to increase our ability constantly remember God and fear Him.Abudraham (Rabbi David ben Joseph Abudraham ) explains that there are mezuzot that are placed in the home, and there are mezuzot for a city and country.The mezuzot in our homes remind us of God’s tremendous gift to us – the land of Israel.According to Aruch HaShulchan, the mezuza contains the unification of God’s Holy Name which, when we contemplate it, maintains our fear of Heaven and keeps us from sinning.Rabbi Samson Rafael Hirsch explains that in fulfilling this mitzva we hallow our homes as places where God is ever-present and where the service of God is fulfilled.By doing so, we testify that our entire lives are accomplished through God. We attest that all that happens to us in life is through God.All of the above reasons point to the fact that this ever-present reminder within our lives of God and His Oneness keeps us from losing sight of the larger picture of God’s plan for the universe. It allows us to attain the highest levels of self-fulfillment.Although it’s important to emphasize that the main reason we perform God’s commandments is simply because this is what God desires of us, in addition to the reasons cited above there are other general reasons provided by the sages for the fulfillment of this mitzva.We must also keep in mind that the highest level of mitzva observance is to do so with no regard to the reward that one receives (Pirkei Avot 1:3).The Talmud (Menachot 33b) states: “Rabbi Chaninah said: Come and see how the qualities of the Holy One blessed be He are different from those of flesh and blood. It is the nature of human beings to have the master sit in the house while the servants stand guard outside. Not so is the nature of the Holy One Blessed be He! His servants sit inside while He stands guard outside.”Indeed, no less an authority than the author of the Shulchan Aruch, Rabbi Yosef Karo, writes in his Kesef Mishna that the mezuza has protective qualities. He writes however that this protection only comes with the actual observance of the mitzva and not through the parchment itself.The Maharam of Rottenburg, a very early authority from the era of the Rishonim, is quoted both by the Tur and the Taz (commentaries on the Shulchan Aruch) as writing that “before he affixed a mezuza between the Beit Midrash and his home, a ruach rah [evil spirit] would disturb him while he was taking his afternoon nap.”When a person places the mezuza upon his doorway, God guards him from damaging spiritual forces known as mazikin as well as from other dangers. MeShiurei HaRishon LeTzion IV section 169 writes that when there is a kosher mezuza on the door post the home is guarded by 60 angels and the Name of God barring the entry of any damaging spiritual force. See also Rabbi Ovadia Yosef in Yabia Omer (Volume 8 YD section 30) who cites a proof to this from the Jerusalem Talmud.Besides protection, the reward for observing this mitzva is also very great. If one is careful in the performance of this mitzva, he and his descendants will merit long life. The converse, however, is also true (See Shulchan Aruch 285:1; Tur; Sifrei Aikev Piskah 46; See also Shabbat 32b regarding the sin of being neglectful in this mitzva).And there are other physical rewards, as well. The Talmud (Shabbos 23b) tells us that one who is careful in the mitzva of mezuza merits a beautiful home. This can be attested to by the experience of many people.The Tur describes the protective quality as greater than the fact that the mezuza extends life perhaps because the protection quality is an open miracle, while the longer life is a hidden miracle (Beit Yosef).Alternatively, the wondrous aspect of a king watching over his servants is why it is described as greater (Beit Yosef and Bach).According to the Sefer Haredim (introduction), one who purposefully lives in a home (such as a tent) where he is fully exempt from observing the mitzva of mezuza will not be saved during a period of Divine wrath (beidna derischa). This is also found in the Shla’s (Rabbi Isaiah Horovitz) commentary to the Babylonian Talmud, Tractate Hullin, based upon Tractate Shabbat 32b.The Baal HaTurim explains that the Torah juxtaposed the “Shema” section in the Torah to the section of, “And it shall be when God shall bring you to the land” (Deuteronomy 6:10) to teach us that it is in the merit of observing the mitzvot of a Sefer Torah, tefillin and mezuza that we will inherit the land without effort.It was also the mezuza and Onkelos’ meticulous observance of this mitzva that was paramount in the incident of the conversion of the Roman caesar’s men recounted in the Talmud (Avoda Zara 11b). Onkelos the son of Klonimus converted to Judaism. Caesar, his uncle, sent a legion of Roman soldiers to retrieve him. Onkelos enticed the soldiers to Judaism by quoting verses, and they converted. The caesar sent a new legion but this time he instructed them not to enter into conversation with his nephew. As they dragged him from his home, Onkelos saw the mezuza affixed to his doorpost. He longingly placed his hand upon it and asked them, “Do you know what this is?” The soldiers could not contain their curiosity and answered, “You tell us.”Onkelos explained the unique nature of this mitzva, as referred to above: “It is the nature of human beings to have the master sit in the house while the servants stand guard outside. Not so is the nature of the Holy One Blessed be He! His servants sit inside while He stands guard outside. As it states [Tehillim 21:8], ‘God Shall guard your departure and arrival, from now and forever more.’” They too converted, and caesar did not pursue the matter further.In summary, we see from sources throughout the Babylonian Talmud, the Jerusalem Talmud, the Rishonim and the Shulchan Aruch that the mezuza indeed offers protection from damaging spiritual forces, from sin and from other dangers. Moreover, it offers long life for us and for our children, the reward of beautiful home, and the land of Israel itself.The author, a rabbi, is the author of 11 books on Jewish law, including, Mezuzah A Comprehensive Guide, as well as the Not Your Usual Halachah series. His books are available on Amazon.com and have approbations from leading Torah scholars of the generation.