Understanding Kinot

On Tisha B’Av (the 9th of Av), Jews gather in synagogues to mourn the destruction of the Beit HaMikdash (the ancient Temple). Both at night and the following morning, we recite kinot (elegies) that reflect upon themes of tragedy and loss, getting us into the experience of mourning.

Kinot follow the example of Megillat Eichah, written by the prophet Jeremiah after the destruction of the first Temple. The first kinot were written to mourn the events surrounding the Destruction and the subsequent exile. More were added when the second Temple was destroyed 490 years later. 

What is the Puripised of Kinot? What makes it so hard to get?