It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said during the Farewell Hajj: "Listen! Which month do you consider the greatest in sanctity?" They replied: This month of ours (Dhu al-Hijjah). Then he said: "Which city do you consider the greatest in sanctity?" They replied: This city (Makkah). He (peace and blessings be upon him) said: "Do you know which day is the greatest in sanctity?" They said: This day of ours (the day of Hajj). He (peace and blessings be upon him) said: "Allah has made sacred for you your blood, your wealth and your honour, except by right, just like the sanctity of this day of yours in this city of yours. Listen! Have I conveyed (the message of Allah)?" He asked this three times, and all of them answered yes.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العارية / 11493