The occasion called Arbaeen occurs 40 days after Ashura, the tenth day of the lunar calendar month of Muharram, when Imam Hussein (AS), the grandson of Prophet Muhammad (PBUH) was martyred at the hands of the tyrant of the time, Yazid I, back in the seventh century.
The Culture House of the Islamic Republic of Iran in Mumbai, India, has prepared the following video clip on the magnificent Arbaeen pilgrimage.