اربعین

The number 40 carries weight across Iranian culture, both Islamic and pre-Islamic. The 40-day mourning period is observed for ordinary deaths as well: the چهلم (chehelom, fortieth-day memorial) is a major commemoration on the 40th day after a relative's death, with a meal served, prayers read, and visitors received. Forty also appears in Persian mysticism, the چله (chelle, 40-day spiritual retreat) practiced by Sufis, and in folk tradition, the چله بزرگ (chelle-ye bozorg, the long forty days of winter). Arba'in for Hossein is the same number, scaled to the central tragedy of Shia history.