Learning the laws of Beis Habechira/The Temple:
The Midrash states that studying the laws of the Beis Hamikdash, its structure and vessels, is viewed by Hashem as if one is building the Temple. This means to say, that during times of exile when one is unable to help build a physical Temple, one fulfills the eternal Biblical command of “Making me a Temple” through studying the laws of the Temple. One should study the prophecies in Yechezkal from 40 and onwards, Miseches Middos, and Hilchos Beis Habechira of the Rambam. One should especially increase in studying these laws during the period of Bein Hametzarim. Studying these laws weakens the exile and hastens the redemption.
Rambam Beis Habechira-Chapter 1: The Temple
Halacha 1: The Mitzvah to build a Temple
- The Mitzvah and its purpose: It is a positive commandment to construct a House for God for a) the sake of offering sacrifices and b) for the Jewish people to visit it three times a year to celebrate there [by the Shalosh Regalim].
- The Mishkan in the times of Moshe: The Mishkan in the times of Moshe was merely temporary [and hence did not fulfill the above command for eternity, and rather the Mitzvah continues to apply until the Temple in Jerusalem is built].
Halacha 2: The history of the Mishkan and Temple until the Temple was built in Jerusalem
- Gilgal: After the Jews entered Israel they erected the Mishkan [of Moshe] in Gilgal throughout the fourteen years in which they conquered and divided the land.
- Shiloh: From there, they came to Shiloh, and built a house of stone, and spread the curtains of the Mishkan over it.
- It did not have a roof.
- The sanctuary of Shiloh stood for 369 years.
- When Eli died, it was destroyed.
- Nov: Afterwards, they came to Nov and built a Mikdash.
- When Samuel died, it was destroyed.
- Givon: Afterwards, they came to Givon and built a Mikdash.
- The Mikdash stood in Nov and Givon for 57 years.
- Jerusalem: From Givon, they came to the eternal structure [in Jerusalem].
Halacha 3: Building a Temple in areas other than Jerusalem
- Once the Temple was built in Jerusalem, it became forbidden to build a Temple for God and to offer sacrifices in any other area.
- The Mikdash for all generations is only in Jerusalem, on Mt. Moriah.
 See Likkutei Sichos 18:412; Hisvadyus 5748 2:564; Shulchan Menachem 3:52
 Tanchuma Tzav 14; Pesikta of Rav Kahana 6; Pesikta Rabasi 16; Yalkut Shimoni Yechezkal 43:10
 Toras Menachem 5750 4:55
 See Even Haezel on Rambam ibid; Chidushim Ubiurim p. 17-18 footnote 36