Our fasting does much more than just commemorate the physical destruction of the Temple.

Picture the following scenario, thousands of years ago, when the Jewish people returned to their homeland from seventy years’ exile in Babylon:

The first wave of returnees reached Jerusalem, armed with permission from the Persian king, Cyrus, to rebuild the Temple.  The people returned to their homeland, their holy city, and started life anew. 

Those Jews who remained behind in Babylon turned to the prophet Zechariah and asked: "Should we continue to observe the fast of the Ninth of Av?

They explained their doubts:

"While it is true that the Temple has been rebuilt, but the Second Temple is only a shadow of the First.  The sanctity of the original temple, built by King Solomon, was far greater.  Outwardly, it was far more impressive and imposing.  There is still a great deal to mourn.”

G-d’s reply to their question affords us an insight into the reason that our Sages established fast days in the Jewish calendar.  He asked: “Do you suppose that I need your fasting?  Is it for My benefit?

“You asked whether there is still anything to mourn over, now that the Second Temple is standing.  Read the words of the prophets who rebuked you again and again before the First Temple was destroyed.  Review the list of warnings they gave you about the sins of the nation; that way, perhaps you will come to understand why you lost the First Temple.

“Then ask yourselves: 'Have these transgressions been rectified?'  Have we improved ourselves sufficiently?"

The prophet sums up his reply, which will apply mainly to the generations who merit the complete redemption.

'Thus says the L-rd of Hosts:

The fast of the fourth month, and the fast of the fifth, and the fast of the seventh, and the fast of the tenth, shall be joy and gladness to the house of Judah, and cheerful seasons; therefore love ye truth and peace.   

Zecharia 8:19

All the fast days will be annulled when the nation attains its sublime goal: “Love peace and truth.”

The First Temple was destroyed because people were not devoted to Truth.  Idol worship spread among the people, and with it, undermining the high ethical standards of the nation.

During the period of the Second Temple, the situation was better in this aspect.  Israel was not drawn into idol worship; they clung to the Truth.  However, during the same period of history, their pursuit of peace among their fellow men fell short of the high standards that Heaven asks of the Jewish people.

This shortcoming plagues the Jewish People yet today, and is the reason that we are still in exile, and continue to observe the four annual fasts.

The prophet teaches the Jewish People: We fast not to only to recall the physical destruction of the Temple, but also – and perhaps, even more – to rectify the flaws in our character, for they are the spiritual cause of our suffering.

If we have achieved Truth at the expense of Peace, or Peace at the expense of Truth, we must continue with our annual fasts, for the seeds of the destruction are still germinating within us.

How much more do we need to fast, if we find ourselves flawed in both areas!  When will our trials end?  When we succeed in eradicating all traces of falsehood and hypocrisy, only when Truth will reign and Peace will be firmly established.

Then there will no longer be a need for our fasting, and, as the prophet foretells, the days of our mourning will be transformed to seasons of rejoicing.