When the reciters of Qur'an were martyred, Messenger of Allah ﷺ recited Qunut for one month and I never saw him (i.e. Messenger of Allah ﷺ) so sad as he was on that day.
قَنَتَ رَسُولُ اللَّهِ ﷺ شَهْرًا حِينَ قُتِلَ الْقُرَّاءُ فَمَا رَأَيْتُ رَسُولَ اللَّهِ ﷺ حَزِنَ حُزْنًا قَطُّ أَشَدَّ مِنْهُ