The day of Arafat (or Arafah) is the 9th day of the month of Dhul Hijjah on the Islamic calendar. It occurs near the end of the Hajj pilgrimage as pilgrims stand on the plain of Arafat to perform prayers, supplications, and acts of worship.
Allah perfected the religion of Islam for Muslims on the day of Arafat. It is also the day on which the Prophet (PBUH) delivered his last sermon usually referred to as his Farewell Sermon (in Arabic: Arabic: خُطْبَةُ الْوِدَاع, Khuṭbatu l-Widāʿ), in which he affirmed the sanctity of human life and the abolition of racism. This sermon included the Verse of the Perfection of the Religion (in Arabic آیَة إِکْمَال الدِّيْن, Āyat Ikmāl ad-Dīn):
"This day have I perfected your religion for you, completed My favor upon you, and have chosen for you Islam as your religion." (Surah Al Ma'idah, 5:3)
In normal years, over 2.5 million pilgrims or more visit the plain of Arafat during Hajj, the annual pilgrimage to Makkah, Saudi Arabia. This represents the finale and climax of the Hajj journey, the pilgrims' most important ritual.
Abdu Rahman ibn Ya'mar reported: The Messenger of Allah (Peace and Blessings Be Upon Him) said: "The Hajj is Arafat. Whoever reaches the night of Arafat before the rising of the sun at dawn the next day, has completed his pilgrimage." (Sunan al-Nasa'i)
The Prophet compared Arafat Day to a day of celebration (Eid). While it is not technically Eid, it is a celebration since it marks the end of successfully completing the annual Hajj journey. It should be a joyful moment, as well as a time of reverence and dedication.