The Messenger of Allah ﷺ performed the qunut for a month after the reciters were killed, and I never saw the Messenger of Allah ﷺ grieve more deeply than he did then.
قنت رسول الله ﷺ شهرا حين قتل القراء، فما رأيت رسول الله ﷺ حزن حزنا قط أشد منه.
Bukhari narrated it in the Book of Funerals (1300) from Amr bin Ali, who said, Muhammad bin Fudayl narrated to us, who said, Asim Ahwal narrated to us, from Anas, and he related it. Muslim also included it in the Book of Mosques (302/677) through another route from Asim, in similar wording.