20th Safar AH is the day of Arbaeen or Chehlum of Imam Hussain (AS) and 40th day after Ashura. The Purpose of Imam Hussain’s (AS) mission is very well summarised in the Ziyarat of Arbaeen.
According to Imam Hasan bin Ali Al Askari (AS) The signs of a true believer are five:-
1) Recite 51 Raka’t Salaat during the 24 hours of the day (17 Raka’ts obligatory, + 34 Raka’ts in Naafilah Salaats),
2) Be in Karbala for Ziyarat of Imam Hussain (AS) and other martyrs, or at least recite Ziyarat of the Holy Imam as given below,
3) To wear a ring in the right hand,
4) To put the forehead on the earth (preferably on the earth of Karbala) in prostration,
5) To pronounce “Bismillahir-Rah’maanir-Rah’eem” in clear and loud voice while praying the Salaats.
As reported by Shaykh al-Tusi, in Tahdhib al-Ahkam and Misbah al-Mutahajjid, Safwan al-Jammal said: “My master al-Sadiq, Allah’s blessings be upon him, instructed me to visit Imam al-Hussain (AS) on the Arbaeen Day, in the early forenoon, and to say the following words: