Musnad Ahmad 962:25

Zayd ibn al-Hubab narrated to us, Mu'awiyah ibn Salih narrated to us, Sulaym ibn 'Amir narrated to me, he said: I heard Abu Umamah say: I heard the Messenger of Allah (peace and blessings of Allah be upon him) addressing the people during the Farewell Pilgrimage while he was upon al-Jad'a' (his she-camel), placing his foot in the stirrup of the saddle, stretching himself, saying: "Do you not hear?" A man from the end of the people said: "What are you saying?" He said: "Worship your Lord, pray your five (daily prayers), fast your month (Ramadan), pay the Zakat of your wealth, and obey those in authority over you; you will enter the Paradise of your Lord." I said to him: "How long ago did you hear this hadith, O Abu Umamah?" He said: "When I was thirty years old."