The late Ayatullah Al-Hajj Sheikh Abdul Karim Haeri, the founder of the Hawzah Ilmiyyah of Qum recounts: “During the time when I was engaged in religious studies in the city of Samarra, an epidemic, in the form of plague, spread amongst the inhabitants of the city and everyday several people would die of the disease.
One day, some of the inhabitants of Samarra had gathered in the house of my teacher, the late Sayyid Muhammad Fisharki, when Ayatullah Mirza Muhammad Taqi Shirazi (d. 1338 ah), who, in terms of knowledge, was at par with the late Sayyid Fisharki, suddenly arrived. In the course of the conversation, the talk drifted towards the issue of the plague that had threatened the lives of all the people.
The late Mirza said: “If I were to issue a hukm (ruling), would it not be mandatory for it to be executed?” All those present said: “Yes.” He said: “I rule that from today onwards, for a period of ten days, the entire Shiite community of Samarra should recite “Ziyarat Ashura” and gift the rewards of this recitation to Hadhrat Narjis Khatun – the mother of Imam Mahdi (a.s) – in order that this calamity is repelled from them.”
Those present in the gathering informed the other Shiites of this ruling and all of them engaged themselves in reciting the “Ziyarat Ashura.” The following days onward, it was observed that none of the Shiites would die due to the disease whereas the non-Shiites continued to suffer deaths – and this became plainly manifest for all the inhabitants of the city, such that some of the non-Shiites used to question their Shiite friends: “How is it that our people die due to the disease, whereas there are no deaths on your side?”
The Shiites would answer: “All of us recite “Ziyarat Ashura” of Imam Husain (a.s) in order to remain protected from the epidemic and Allah wards away the calamity from us!” ( Dastanha-e-Shigeft, pg. 323 )