mezuzah

mezuza puhekieltä A piece of parchment inscribed with Pentateuchal texts and attached in a case to the doorpost of a house, in accordance with Jewish law, that says that “the Jews must remember the Tenth plague Plague and the blood on the doorposts.”
1973, Thomas Pynchon, Gravitys Rainbow'':

Slothrop gives him the mandala. He hopes it will work like the mantra that Enzian told him once, mba-kayere (I am passed over), mba-kayere…a spell against Marvy tonight, against Tchitcherine. A mezuzah. Safe passage through a bad night

When Manny or either of his parents went through their front door they put a finger on their lips and then to the mezuzah on the door frame.