Aga Nasiri, who was the among close companions of Ayatullah Hujjat Kuh Qamrahaye and Aga Gul Muhammadi Abhari narrate this incident. (There are others who have also related this incident).
It was a period of drought. The people were anxious and had no idea about what to do. The students (tullaab) were also worried since their monthly allowance was only 10 tuman, while only a roti came for one tuman.
Finally Ayatullah Hujjat Kuh Qamrahaye summoned forty students to go to Masjid Jamkaran. Each of them was to recite Ziyarat Ashura and seek relief from Imam Musa al Kazim (a.s.), Abul Fazal Abbas (a.s.) and Janabe Ali Asgar (a.s.). These forty students began recitation the Ziyarat.
It was the blessing of this Ziyarat that, suddenly there were dense clouds and started raining heavily. The drought conditions were eased and the people gained relief from its difficulties.
Miracles of Ziyarat e Ashura – P.E.T Publications