The grandson of prophet Mohammad (PBUH), Imam Hussein (as), and his companions were martyred in Karbala on the 10th of Muharram of the year 680 AD. Arbaeen refers to the 40th day after the martyrdom of Imam Hussein (as). Commemorating the 40th day after a person’s death is a common practice among people, in which they offer food in remembrance of the person. On the day of Arbaeen, people around the world gather together to again remember Imam Hussein (as), offering food and programs. Many embark on a pilgrimage, a number of them on foot, to the Shrine of Imam Hussain (as), as another way of commemorating this day.
The practice of walking towards the shrine became popular after the martyrdom of the Imam, and the first people to visit the burial ground were Jabir ibn Abdullah al-Ansari and Atiyeh Owfi, well-known companions of prophet Muhammad (PBUH). For years caravans from different cities in Iraq, such as Baghdad, Basreh, and mostly Najaf would begin their journey towards Karbala on foot. The walking towards the Shrine of Imam Hussein (as) has many implications including pilgrims expressing their devotion, which arises from the immense amount of love in their heart, or pilgrims claiming how deficient and humble they are compared to the virtues of the person they are visiting.
(From ‘the Encyclopedia of Ashoura’ by Jawad Mohaddessi)