Deuteronomy 6:9

And thou shalt write them upon the posts of thy house, on the door-posts, and on thy gates. This command was later also reduced to a mere outward observance in the Jewish custom of the Mesusah, according to which a piece of parchment containing Deuteronomy 6:4; Deuteronomy 11:13 was placed in a small wood or metal case and fastened to the right door-post of the house.