Each year at this time, we place so much emphasis on Rosh Hashanah and Yom Kippur that we ignore another important day on the calendar – the day after Rosh Hashanah, the third day of Tishrei, the Fast of Gedaliah.

The fast commemorates the murder of a man named Gedaliah ben Achikam nearly 2,600 years ago.

Was Gedaliah a good man or a bad man? Was he a Jewish patriot or a Jewish traitor?

We do not really know. We know he was the man the Babylonians put in charge of Judah after the fall of the First Temple and the vanquishing of the line of David.

We believe he came from a family devoted to the kings of Judah, and that he himself may have served in an official capacity. We believe he was devoted to the God of Israel and His people, but we do not know. We do not know whether he was good for the Jews or bad for the Jews.

All we know for sure is that nearly 2,600 years ago, a religious fanatic named Yishmael ben Netanyahu murdered Gedaliah ben Achikam, ostensibly in the name of God.

And we know something else. When Gedaliah was murdered, life did not “go on” for the Jews.

That murder began a process that, within five years, led to the expulsion of the Jews from their homeland and the beginning of an exile that has continued from that day to this for the majority of us.

It is for this reason that, long before the rabbis came into existence, the people of Israel already marked the day of that murder by fasting and prayer. To this day, the third day of Tishrei, the day after Rosh Hashanah, is known as Tsom Gedaliah, the Fast of Gedaliah. (When that day is a Shabbat, as it is this year, the fast is observed on Sunday.)

There is good reason for this fast. By all rights, the story of the Jewish people should have ended when the Babylonian exile began. Everything we were was rooted in the land – our identity, our culture, our sacred traditions, our modes of worship – but now we were separated from that land.

Other people, similarly disconnected from their native soil and their heritage, disappeared from history. We survived. We had Jeremiah and Ezekiel and Zechariah and many people whose names we do not know – prophets of God and people of vision who were filled with Ahavat Yisrael, love of the people Israel. They would not let us shrivel and die. They would not let us forget who we were or where we belonged.

And we did not.

The Fast of Gedaliah is meant to remind us of the fate we could have suffered, but did not. It is meant to remind us that extremism of any kind carries the most serious consequences and can even lead to total ruin.

That lesson was relearned in the days of the Second Temple, with even more far-reaching consequences. Zealots convinced themselves that they needed only to start a war against the overwhelmingly more powerful Roman occupier; God would end the war quickly – and with total victory for the Jews.

Instead, the war ended with total defeat for the Jews. With that defeat came an end to Jewish sovereignty in the Land of Israel for nearly 2,000 years.

Today, we live in a world filled with extremism of every stripe. Islamic extremists are the greatest threat, but there are Christian extremists, too, and even a few Jewish ones. Any one can set off a chain of events that would lead to disater.

There are the issue-motivated zealots, people such as the so-called “eco-terrorists” and extreme anti-abortionists, who believe that the only way to save the world is to destroy it first, even to the taking of human life.

“Extremism in defense of liberty is no vice,” Sen. Barry M. Goldwater told the Republican convention of 1964. He was wrong. All advocates of extremism, whatever their cause, are wrong.

The need to understand that important lesson is what makes the Fast of Gedaliah so important a day.