A mezuzah (מְזוּזָה "doorpost"; plural: mezuzot) is a piece of parchment inscribed with specific Hebrew verses from the Torah, which Jewish followers of Rabbinical Judaism affix to the doorposts of their homes. These verses are the Biblical passages in which the use of a mezuzah is commanded ( and ); they also form part of the Shema prayer.
In mainstream Rabbinic Judaism, a mezuzah must generally be placed in every doorway in the home, with some exceptions such as bathrooms (which are not a living space) and small closets.
The klaf is prepared by a qualified scribe ("sofer stam) who has undergone training, both in studying the relevant religious laws, and in the more practical parts, i.e. carving the quill and practising writing. The verses are written in black indelible ink with a special quill pen made either from a feather or, now quite rare, a reed. The klaf is then rolled up and placed inside the case.
In the Bible, the word mezuzah only refers to the two 'doorposts' or 'doorjambs' of a door, the upright posts on either side of it which support the lintel, and appears in various contexts unrelated to any religious commandment or parchment. The word later acquired the modern meaning of piece of parchment in post-Biblical Hebrew due to the Deuteronomy commandment above requiring to write verses on doorposts.
The word's origin is disputed:
one accepted understanding derives mezuzah from the root z-u-z () meaning 'motion' or 'shift' (verb zaz () 'to move, deviate, shift'), describing a doorpost as the device enabling the door to move or shift. The root is unused in the Bible but is common in post-Biblical Hebrew and Aramaic, and is considered to have existed in the language then.
another accepted understanding derives mezuzah from the Akkadian word mazzazu 'stand' (like the socle or stand of a column or stele), from the Akkadian verb izuzzu 'to stand', describing a doorpost as the socle or stand of the entrance, as opposed to the moving part, the door which revolves – a description similar to its corresponding Greek translation σταθμός in the Septuagint, which in addition to 'doorpost' generally means 'something fixed, something standing' from ἵστημι 'to stand'.