"And you shall write them upon your doorposts and on your gates" - Deuteronomy 6:9.
For an article elaborating on the Torah sources for the Mezuzah's protective powers, click here.
The following is not a real conversation. But it definitely could have happened.
Jeff: Hey bud, what's up?
Mike: Nothin' much, how you doing?
Jeff: Awesome, you gotta come check out my new place on Columbia.
Mike: Sure man, I'd love to.
Three months later...
Mike: Nice place, dude! I like your sculpture there in the corner.
Jeff: Sculpture? I don't have any sculptures in here.
Mike: So what's that big thing there?
Jeff: That's my laundry, bro.
Mike: @#$%.
Mike: Anyway...where's your Mezuzah?
Jeff: Umm..I think it may have gotten stuck in middle of the sculpture..
Mike: Well then, why don't you just call the rabbi and ask him to bring a new one over?
Jeff: He'll really do that?
Mike: Listen man, he isn't a snobby CEO guy, he loves doing this stuff.
Jeff: Wow. Let's do it. How does it work?
Mike: You call/text/email him. He'll bring it over. You can either buy it or borrow it. Either way you put down $40. If you want to buy it, that's the end of the story and you take it with you when you move. If you don't, just bring it back to him at the end of the term, and if it's all in one piece he gives you the $40 back.
Jeff: faints out of sheer excitement.
Get your Mezuzah today!