We are currently deep into the "dog days" of the Jewish calendar—known as the "Three Weeks." We avoid celebrations, revelry and music, and focus instead on the destruction of the Holy Temples and our current state of exile.

Rabbi Yosef Yitzchak Schneersohn, the sixth Lubavitcher Rebbe, would say, "One deed is more valuable than one thousand sighs." As such, during this period we cannot suffice with mourning and sorrow; more importantly, it is incumbent upon us to try to correct the mistakes which originally caused this two-millennium-long national tragedy. Let us turn to the words of our sages to discover the cause of this seemingly interminable and persecution-filled exile.

The Talmud1 explains why the Babylonian exile, which followed the destruction of the first Temple, lasted only a predetermined seventy years, while we languish in this current exile for so much longer, with no given end-date: "The first ones, whose sins were known, the end [of their exile] was made known. The latter ones, whose sins were not known, their end is [also] unknown."

The unique nature of hatred and fighting: it is the "unknown sin"This statement apparently contradicts another statement cited on the very same folio of the Talmud: "Why was the first Temple destroyed? Because of three sins of which the Jews were guilty: idolatry, sexual indiscretions and murder. The second Temple – when Jews were involved in Torah, mitzvot and acts of kindness – why was it destroyed? Because Jews were guilty of harboring baseless hatred towards each other!"

Wanton hatred is very noticeable. How can the Talmud say regarding a society where such behavior was rampant that "their sins were not known"?

The Rebbe explains that this is the unique nature of hatred and fighting: it is the "unknown sin." On average, an idolater, adulterer, or murderer is keenly aware of his sin. People fall victim to temptation, but repentance is eminently achievable because the person himself is conscious of and troubled by the sins which defile his soul. However, the person who is guilty of participating in quarrels and hatemongering rarely believes that he is at fault. In his estimation, the other party rightly deserves all the abuse being heaped on him! Thus, while baseless hatred is perhaps the most overt of sins, so few actually recognize their own guilt.

This is true both in our interpersonal relations as well as our nation's regrettable tendency to be heavily preoccupied with inter-faction squabbles. Left, Right, and Center. Conservative, Orthodox, and Reform. Chassidic, Zionist and anti-Zionist. And the list goes on…

It is easy to blame "them" for factionalism and divisiveness; it is much harder to find the faults within ourselves. But the Redemption will come when we finally recognize that – even if in fact "I'm right and he's wrong" – there is never a valid reason to hate a fellow Jew.