We have entered a three-week period of mourning, between the fasts of the 17th of Tamuz and the 9th of Av, commemorating the destruction of Jerusalem and the Holy Temple.  We keep various mourning customs during this period.

Ever since the destruction and dispersal of the Jewish People in exile, we have been animated by a single hope, in the coming of Moshiach and the rebuilding of the Temple.  This faith has sustained us through the long and bitter years of exile, and has enabled us to remain a cohesive nation.  Other nations, far larger and more powerful, have disintegrated, while the Jewish People, although scattered throughout the world, remains.  Throughout our exile, we drew strength from G-d's promise to gather us up and bring us back to Jerusalem to rebuild the Holy Temple.

We have never forsaken our faith and trust in the ultimate Redemption.  Although nearly 2,000 years have passed, we continue to await Moshiach's arrival.  Our faith is steadfast despite numerous challenges and upheavals.  In fact, our faith alone enabled us to weather the many difficulties we have faced.

G-d did not only give us a promise that He would redeem us.  He also gave us support and encouragement.  The Midrash (Yalkut Shimoni, Yechezkel 40:4) relates:  "When G-d revealed Himself to Ezekiel and showed him the structure of the Third Temple, [Ezekiel] said to Him:  My master, are they able to build it now, that you say to them, 'and you shall make it?'  G-d answered:  Let them read about the structure of the Temple, and I will consider it as if they are building it!"

G-d promised that through studying the laws pertaining to building the Temple, He considers it as if we are building the Temple in actuality.  Although, as yet, we are unable to physically build the Temple, G-d gave us a means to satisfy our longing for the Holy Temple and hasten its completion. 

In truth, any mitzvah we do or any Torah we study adds to our merit and hastens the Redemption.  However, studying the laws of the Temple building has an added quality, since G-d has given us a special power to rebuild the Temple spiritually in this manner.  The words that we speak bring the Holy Temple into existence in spiritual realms.

The Rebbe initiated the custom of studying the laws of building the Holy Temple during the three-week mourning period.  Through this learning, we somewhat lessen the anguish over our loss of the Temple, and replace it instead with an urgent anticipation for the complete Redemption.