Musnad Ahmad 670:2

Waki’ narrated to us, Sufyan narrated to us, from Bukayr ibn ‘Ata’ al-Laythi, who said: I heard ‘Abd al-Rahman ibn Ya’mar al-Dayli saying: I witnessed the Messenger of Allah (peace and blessings of Allah be upon him) while he was standing at ‘Arafat. People from the people of Najd came to him and said: "O Messenger of Allah, how is the Hajj?" He said: "The Hajj is ‘Arafat. Whoever comes before the dawn prayer of the night of Jam’ (Muzdalifah), his Hajj is complete. The days of Mina are three days; whoever hastens in two days, there is no sin upon him, and whoever delays, there is no sin upon him." Then he had a man ride behind him, and he began to call them out.