On the third of Tishrei, Gedalia b. Aĥikam was killed. After the First Temple was destroyed and most of the Jewish people were exiled to Babylonia, the king of Babylonia appointed Gedalia b. Aĥikam to govern the Jews who remained in Judea. The Jewish people as a whole hoped that this surviving remnant, by reestablishing themselves in Eretz Yisrael, could rebuild the Temple and reestablish Jewish sovereignty, together with those who would eventually return from Babylonia after seventy years of exile. Indeed, for some time it seemed that the meager population that remained in the land was recovering from the Temple’s destruction and beginning to cultivate fields and vineyards.

However, the king of Ammon, who wanted to eradicate the remnant of Israel, sent Yishmael b. Netania to murder Gedalia. Yishmael had an additional, personal reason to carry out the scheme: He was a member of Judea’s royal family, and he thought that he should govern Judea instead of Gedalia. Several military officers warned Gedalia about Yishmael and even recommended killing him before he could carry out his plan. But Gedalia did not believe them, accusing them of maligning Yishmael.

In the seventh month, Yishmael ben Netania ben Elishama, who was of royal descent and had been one of the king’s officers, came with ten men to Gedalia ben Aĥikam at Mitzpa; and they ate together there at Mitzpa. Then Yishmael ben Netania and the ten men who were with him arose and struck down Gedalia ben Aĥikam ben Shafan with the sword and killed him…along with all the Judeans who were with him…and the Chaldeans who were there. (Yirmiyahu 41:1-3)

This extinguished the last ember of Jewish sovereignty in Eretz Yisrael and realized the full measure of exile. This is why the prophets instituted a fast day.