It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) addressed them during the Farewell Hajj and said: "Listen! Allah has made your blood and your wealth sacred to you just as the sanctity of this day of yours, in this city of yours, in this month of yours. Listen! Have I conveyed?" The Companions said: Yes. He (peace and blessings be upon him) said: "O Allah, bear witness." He (peace and blessings be upon him) said this three times, then said: "Beware, do not become disbelievers after me, some of you striking the necks of others."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13279