Musnad Ahmad 702:1

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 ‘Arafah. People from the people of Najd came to him and said: "O Messenger of Allah, how is the Hajj?" The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Hajj is the Hajj of ‘Arafah. 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 (the Prophet) had him ride behind him, and he began to proclaim these (words).