The Arbaeen is one of the most significant religious gatherings in the world, marking the end of the 40-day mourning period after Ashura, the day on which Imam Hussein, the grandson of Prophet Muhammad, was martyred in the Battle of Karbala in 680 AD. This pilgrimage, which takes place annually in the city of Karbala, Iraq, draws millions of Shia Muslims from around the globe. It is a powerful symbol of faith, unity, and humanity.
https://muslimmirror.com/arbaeen-a-symbol-of-unity-faith-and-humanity/