Musnad Ahmad 482:111

Yahya ibn Adam narrated to us, Ibn al-Mubarak narrated to us, from Haywah ibn Shurayh, from Yazid ibn Abi Habib, from Abu al-Khayr, from Uqbah ibn Amir: That the Messenger of Allah (peace and blessings of Allah be upon him) prayed over the martyrs of Uhud after eight years, like one bidding farewell to the living and the dead. Then he ascended the pulpit and said: "I am your predecessor (fartukum), and I am a witness over you. Your appointed meeting place is the Hawd (the Cistern), and I am looking at it right now. I do not fear that you will commit shirk—or he said: kufr—after me, but I fear for you the world, that you will compete with one another for it."