Hazrat Saeed bin Al-Musayyib says that whoever attains the standing at Arafah before the break of dawn has attained Hajj.

Hazrat Urwah bin Mudarris at-Ta'i performed Hajj during the time of the Noble Prophet (peace and blessings be upon him). He could not find the people except when they were at Muzdalifah. Then he presented himself in the noble service of the Noble Prophet (peace and blessings be upon him) and said, "O Messenger of Allah (peace and blessings be upon him)! I followed my own desire and exhausted my mount, and by Allah, I did not leave any hill except that I stayed upon it. Has my Hajj been completed?" The Noble Prophet (peace and blessings be upon him) said: "Whoever performed this prayer with us and proceeded from Arafat towards Mina before that, during the day or night, indeed his impurity has been removed and his Hajj has been completed."

It is narrated from Hazrat Abdur Rahman bin Ya'mar that he says: I heard when the Messenger of Allah (peace and blessings be upon him) was staying in Arafat, and people from among the people of Makkah were coming to him. They submitted, "O Messenger of Allah (peace and blessings be upon him)! How is Hajj performed?" The Prophet (peace and blessings be upon him) said: "Hajj is (standing at) Arafat. So whoever comes to Arafat on the night of gathering before the rising of dawn, his Hajj is complete. There are three days in Mina, so whoever hastens in two days, there is no sin upon him, and whoever delays, there is no sin upon him either." Then the Prophet (peace and blessings be upon him) made a person his companion on the ride, who was announcing these words.