Also known as the Day of Arafah  is an Islamic holiday that falls on the 9th day of Dhu al-Hijjah of the lunar Islamic Calendar. It is the holiest day in the Islamic calendar, the second day of the Hajj pilgrimage, and the day after is the first day of the major Islamic holiday of Eid al-Adha. At dawn of this day, Muslim pilgrims will make their way from Mina to a nearby hillside and plain called Mount Arafat and the Plain of Arafat. It was from this site that the prophet Muhammad gave one of his last sermons in the final year of his life. Some Muslims hold that part of the Quranic verse announcing that the religion of Islam had been perfected was revealed on this day.

On 9 Dhu al-Hijjah before noon, pilgrims arrive at Arafat, a barren plain some 12 mi east of Mecca, where they stand in contemplative vigil: they offer supplications, repent and atone for their past sins, seek mercy of God, and listen to Islamic scholars giving sermons from near Mount Arafat. Lasting from noon through sunset, this is known as ‘standing before God’ (wuquf), one of the most significant rites of Hajj. At Namrah Mosque, pilgrims offer Zuhr (Dhohr) and Asr prayers together at noon time. A pilgrim’s Hajj is considered invalid if they do not spend the afternoon on Arafat.

Here are more resources on Arafat: