Tzom Gedaliah (Fast of Gedaliah ) is an annual fast day instituted by the Jewish Sages to mark the assassination of Gedaliah Ben Achikam, the Governor of Israel during the days of Nebuchadnetzar, the King of Babylonia.
In the Prophetic Writings this fast day is called “The Fast of the Seventh” because Tishrei is the seventh month of the Jewish calendar.
In the time immediately after the destruction of the Beit HaMikdash (Holy Temple) and of Jerusalem itself by the armies of Nebuchadnezzar most of the Jewish people who lived in the land of Judah were exiled. There were a a few that remained.
Nebuchadnezzar appointed a man named Gedaliah as his governor. Gedaliah was a tzadik, a good and righteous man. He, together with other righteous leaders, like the prophet Jeremiah, advised the people to accept the Babylonian rule and instead to work towards reestablishing normal life in the country.
Unfortunately, there were people who disagreed with them. A man named Yishmael ben Nesanyah, a descendant of the royal family, murdered Gedaliah and many other Jews. This murder was the final blow that completely destroyed the last remnant of organized Jewish community in the land of Israel till the Jews returned to build the second Beit HaMikdash.
The story of Gedaliah is told to us in two place in the Tana’ch, in Kings II chapter 25 and in the book of Jeremiah chapters 40 and 41.