There are many Jews who believe that the mezuza has some “power” of protection. Ask these people if you can light a match to a mezuza and it should not burn, and they will respond, “of course it burns.” Our obvious response, “If a mezuza cannot protect itself, how can it protect anything outside itself?”
Foolish people who look to the mezuza for physical protection have already been admonished by Maimonides, (Hilchos Mezuza, 5:4). There, he calls such people fools for seeking protection. He states that they take a command, which is in fact for the lofty purpose of guiding us towards profound ideas on the Unity of God, His love and His service, and they make it into an amulet of benefit. Maimonides states they have no share in the next world.
These unfortunate individuals make the same error as those who wear red bendels. Just as the Tosefta in Talmud Sabbath (Chap. 7) says red strings on fingers are prohibited, so too those who mock God’s command of mezuza. I would like to quote the Shulchan Aruch, in the Gilyon M’harsha, Yoreh Daah, 289, page 113 on the bottom, “if one affixes the mezuza for the reason of fulfilling the command, one may consider that as reward for doing so he will be watched by G-d. But, if one affixes the mezuza solely for protective reasons, it in fact has no guidance, and the mezuza will be as knives in his eyes”. These are very strong words from this very well known Rabbi. But what is his lesson? He is teaching us that God is the only source of protection, and that physical objects have no power. Rather, if one feels they do, these objects, even a mezuza, will be the opposite, “knives in his eyes” - something destructive. We say every day, “He (God) alone is the master of wonders”. Do we not listen to ourselves as we pray?
It is of the utmost importance that above all, we have the correct notion of God. He alone is the only source of power in the universe. Magic, enchanters, psychics, voodoo, etc., are all hoaxes. Even the Egyptian astrologers of old were correctly explained as having used slight of hand. (Saadia Gaon in “Emunos v’Daos”) There is no such thing as witchcraft. God’s distinction is exclusive. To assume other powers in the universe means to assume a diminution in God.
I would add one important observation: The notion that mezuzas have powers is actually the opposite of its real purpose. Mezuza, tefillin and tzitzis serve to take man’s investment of security in physical objects, and redirect it towards God. Man invests strength in his limbs, ego in his clothing, and security in his home. God commands us to realize our error, and redirect our security towards Him alone, as this is the truth, and our thoughts are false. We are to remind ourselves of God as we enter our homes and see the mezuza. We reflect on our frail bodies as we don tefillin. And we loosen the grip of the ego as we incorporate tzitzis into our wardrobe. Maimonides groups mezuza, tefillin and tzitzis under one heading, and I believe it is for this reason. Similarly, leprosy strikes one’s home, then his clothing, and finally one’s body - the same three objects. The purpose? To teach a sinful individual that he is a victim of evil speech. But God teaches man in a merciful fashion: first, through objects of his identification before attacking his body. Identification is closely related to security.
If we understand the mitzvos by in depth study as God desires, we will protect ourselves from all foolish notions, which unfortunately circulate with appeal among our brethren. As long as one abandons Torah study and simply “follows the leader”, Jews will remain victims of nonsensical notions and forfeit their “World to Come.” Only he or she who uses their mind will learn what is real, and will abandon that which is false, and which the Rabbis collectively admonished us to repel.