Al-Haafiz Ibn Katheer (may Allaah have mercy on him) said: Every Muslim should mourn the killing of al-Husayn (may Allaah be pleased with him), for he is one of the leaders of the Muslims, one of the scholars of the Sahaabah, and the son of the daughter of the Messenger of Allaah (peace and blessings of Allaah be upon him), who was the best of his daughters. He was a devoted worshipper, and a courageous and generous man. But there is nothing good in what the Shi’ah do of expressing distress and grief, most of which may be done in order to show off. His father was better than him and he was killed, but they do not take his death as an anniversary as they do with the death of al-Husayn. His father was killed on a Friday as he was leaving the mosque after Fajr prayer, on the seventeenth of Ramadaan in 40 AH. ‘Uthmaan was better than ‘Ali according to Ahl al-Sunnah wa’l-Jamaa’ah, and he was killed when he was besieged in his house during the days of al-Tashreeq in Dhu’l-Hijjah of 36 AH, with his throat cut from one jugular vein to the other, but the people did not take his death as an anniversary. ‘Umar ibn al-Khattaab was better than ‘Ali and ‘Uthmaan, and he was killed as he was standing in the mihraab, praying Fajr and reciting Qur’aan, but the people did not take his death as an anniversary. Abu Bakr al-Siddeeq was better than him but the people did not take his death as an anniversary. The Messenger of Allaah (peace and blessings of Allaah be upon him) is the leader of the sons of Adam in this world and the Hereafter, and Allaah took him to Him as the Prophets died before him, but no one took the dates of their deaths as anniversaries on which they do what these ignorant Raafidis do on the day that al-Husayn was killed. … The best that can be said when remembering these and similar calamities is that which ‘Ali ibn al-Husayn narrated from his grandfather the Messenger of Allaah (peace and blessings of Allaah be upon him), who said: “There is no Muslim who is afflicted by a calamity and when he remembers it, even if it was in the dim and distant past, he says Inna Lillaahi wa inna ilayhi raaji’oon (verily to Allaah we belong and unto Him is our return), but Allaah will give him a reward like that of the day when it befell him.” Narrated by Imam Ahmad and Ibn Majaah
al-Bidaayah wa’l-Nihaayah (8/221).