It is narrated from Sayyiduna Abd al-Rahman bin Ya'mar al-Dili (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Hajj (at its core) is standing at Arafah (or: Arafat). So whoever reaches Arafah before the break of dawn has attained the Hajj. The days of staying at Mina are three; so whoever hastens (and leaves) in two days, there is no sin upon him, and whoever delays, there is no sin upon him either." This hadith is sahih (authentic), but the two Shaykhs (Bukhari and Muslim) did not record it.