Rámbám látszik elsődleges forrásnak:
A dwelling which has many doorways requires a mezuzah for each and every doorway, even though one generally enters and leaves through only one of them.
A small entrance between a dwelling and a loft requires a mezuzah. When there is a separate room in a house, or even one room which leads to another room, it is necessary to affix a mezuzah on the doorway to the innermost room, the doorway to the outer room, and the doorway to the house, since all of them are used for the purpose of dwelling and are permanent structures.
Sulchán Áruch is ezt hozza:
A house that has many doorways, even though he normally only exits and enters through one of them one, he is required to make a Mezuzah on each one. Rema: Since they are made for entry and exit. (Thus seems to say the Tur) A cellar that has an entry from the street, where they bring in wine in large barrels and it has a doorway from the house through which they enter and exit it constantly: If the small doorway [inside] is fit to have a mezuzah, then it requires it and the large doorway [outside] is exempt. But if the small one is not fit to have a mezuzah, then the large one requires it and the small one is exempt (Beit Yosef in the name of an Ashkenazi responsum, which is found in Responsae Maharil #99).
Ezt a Gemárát számítják forrásának:
§ Raḥava says that Rav Yehuda says: With regard to a bei harziki, one is obligated to place two mezuzot. The Gemara asks: What is a bei harziki? Rav Pappa the Elder says in the name of Rav: It is a gatehouse that opens to a courtyard, and houses also open directly to the gatehouse. It requires two mezuzot, one for the entrance from the courtyard to the gatehouse, and one for the entrance from the gatehouse to the houses.
Egy szép történet a mezuzáról:
§ The Gemara mentions other Romans who converted to Judaism. It relates: Onkelos bar Kelonimos converted to Judaism. The Roman emperor sent a troop [gunda] of Roman soldiers after him to seize Onkelos and bring him to the emperor. Onkelos drew them toward him with verses that he cited and learned with them, and they converted. The emperor then sent another troop of Roman soldiers after him, and said to them: Do not say anything to him, so that he cannot convince you with his arguments. The troops followed this instruction, and took Onkelos with them.
Azt írja, hogy Máháril itt írja – de én nem látom.
...
Hosszú talmudi szugja, sok egzotikus eset, de a konkrét alapkérdés meglepően sehol.
And Rava says: With regard to these broken entrances [pitḥei shima’ei], which lack the proper form of doorways, one is exempt from the obligation of placing a mezuza. The Gemara asks: What are broken entrances? Rav Riḥumi and Abba Yosei disagree with regard to this. One says that they do not have a proper ceiling, and one says that they do not have lintels [shakofei] above the openings.