Musnad Ahmad 482:106

Hashim narrated to us, Laith narrated to us, Yazid ibn Abi Habib narrated to me, from Abu al-Khayr, from Uqbah ibn Amir al-Juhani, that the Messenger of Allah (peace and blessings of Allah be upon him) went out one day and prayed over the people of Uhud [as he would] pray over the dead. Then he went out to the pulpit and said: "I am a forerunner for you, and I am a witness over you. And I, by Allah, am looking at my Basin (Hawd) right now. And I have been given the keys to the treasures of the earth. And I, by Allah, do not fear that you will commit shirk (polytheism) after me, but I fear for you that you will compete with one another for them."