Who are the weepers of Imam Hussein? Imam Sajad (peace be upon him) said on the pulpit of Shaam: all the trees in the universe, the fishes of the seas, the birds of the air, the mountains, and all the grits of the world have cried for my father. Shedding tears for this pure human will purify you. Imam Sadiq (peace be upon him) says: the one who sits somewhere and cries, his tears and weeping will change into three facts; crying will change into forgiveness, mercy and intercession.
source : erfan.ir