The Fast of Gedalia is a Jewish fast day from dawn until dusk to lament the assassination of the righteous governor of Judah of that name, which ended Jewish rule following the destruction of the First Temple. The Gregorian (civil) date for The Fast of Gedalia varies from year to year but in 2012 this fast day is observed today, September 19th, from dawn until the stars appear at night.
Various prayers are to be said which are pertinent to the holiday and the passages of Vaychal are read from the Torah (Exodus 32:11–14 and 34:1–10).
The fast stems from the time of the Babylonian exile when the Babylonian king Nebuchadnezzar conquered Jerusalem. After the conquest Nebuchadnezzar killed or exiled most of its inhabitants and appointed Gedaliah, son of Achikam, as governor of the now-Babylonian province of Judah. Many Jews who had fled to neighboring lands returned to Judah and tended the vineyards again and enjoyed a new respite after their earlier suffering.
However, Baalis, king of Ammon, was hostile and envious of the Judean remnant and sent a Judean, Yishmael Ben Netaniah, who was descended from the royal family of Judea, to assassinate Gedaliah. In the seventh month (Tishrei) of 582/1 BCE (some four to five years following the destruction of the Temple although there is some disagreement as to the year), a group of Jews led by Yishmael came to Gedaliah in the town of Mitzpa and were received cordially. Gedaliah had been warned of his guests’ murderous intent, but refused to believe his informants, having the belief that their report was mere slander. Yishmael murdered Gedaliah, together with most of the Jews who had joined him and many Babylonians whom the Babylonian King had left with Gedaliah. The remaining Jews feared the vengeance of the Babylonian King (in view of the fact that the King’s chosen ruler, Gedaliah, had been killed by a Jew) and fled to Egypt.
The surviving remnant of Jews was thus dispersed and the land remained desolate. In remembrance of these tribulations, the Jewish sages instituted the ‘Fast of the Seventh’ (see Zechariah 8:19) on the day of Gedaliah’s assassination in the seventh month, a fast still practiced to this day.