The standing at Arafat
On the ninth of Dhu l-Hijja every pilgrim on the Hajj must stand on the plain of Arafat outside Makkah from noon until sunset; the Prophet (s) said that the Hajj is Arafah, and a pilgrim who misses the standing has missed the pilgrimage. The day is spent in prayer and supplication under the open sky, and it was here that the Prophet delivered the sermon of the Farewell Pilgrimage in 10 AH.
Arafah for those at home
Hadith makes the day one of the greatest of the year for all Muslims: a day of forgiveness on which God frees more people from the Fire than on any other. The Shia gather in the afternoon to recite the Supplication of Arafah, the long prayer of Imam Husayn (a) composed on this plain — a meditation on the signs of God in creation and on human need that is among the best-loved texts of the tradition — and the ziyarah of the Imam is especially recommended. Fasting is encouraged unless it would weaken the pilgrim's prayer.
In the events of Karbala
On this day in 60 AH Muslim b. Aqil, the Imam's envoy, was martyred in Kufa, the day after the Imam himself had left Makkah; the majalis of Arafah in many communities recall him.
Written for Shia Online Community. Dates and facts are checked against the references listed below; where the tradition records more than one date, all are given.