ירמיהו, פרק ל״ו, פסוק ט׳

During the fifth year of King Jehoiakim's reign, a large-scale gathering took place as the people united for a public fast. This event occurred during the ninth month, a time of year that would later become known as the month of Kislev [ביאור שטיינזלץ].

To initiate this gathering, a period of fasting was officially decreed and publicly announced to the masses [מצודת דוד]. The call to fast was comprehensive, applying to the entire public present in the capital. It obligated not only the permanent residents of Jerusalem but also the people from the surrounding cities of Judah who had traveled there and were staying within the city walls at the time [מצודת דוד].