Musnad Ahmad 859:1

Abu Sa’id and ‘Affan narrated to us, they said: Rabi’ah ibn Kulthum narrated to us, my father narrated to me, he said: I heard Abu Ghadiyah saying: I pledged allegiance to the Messenger of Allah, may Allah bless him and grant him peace. Abu Sa’id said: So I said to him: With your right hand? He said: Yes. They both said in the hadith: The Messenger of Allah, may Allah bless him and grant him peace, delivered a sermon to us on the day of al-‘Aqabah, and he said: "O people, indeed your blood and your wealth are sacred to you until the day you meet your Lord, like the sanctity of this day of yours, in this month of yours, in this land of yours. Have I not conveyed?" They said: Yes. He said: "O Allah, bear witness." Then he said: "Beware, do not return after me as disbelievers, striking the necks of one another."