Does anyone know what they’re singing?

https://www.instagram.com/p/CRdoZwQHcx-/

I know it’s almost Rosh HaShanah, and they were singing on Tisha b’Av, but I was scrolling my saved stuff on Instagram and remembered this. I can’t make out the words so clearly, but I was hoping someone could point me to what song they’re singing? Thanks.