The Messenger of Allah ﷺ went out one day and prayed over the martyrs of Uhud the funeral prayer, then he turned toward the pulpit and said, "I am your forerunner, and I am a witness over you. By Allah, I am looking at my Pool right now, and I have been given the keys to the treasures of the earth, or the keys of the earth. By Allah, I do not fear that you will associate partners with Allah after me, but I fear that you will compete with one another over worldly gain."
أن رسول الله ﷺ خرج يوما فصلى على أهل أحد صلاته على الميت، ثم انصرف إلى المنبر، فقال: إني فرط لكم، وأنا شهيد عليكم، وإني والله لأنظر إلى حوضي الآن، وإني قد أعطيت مفاتيح خزائن الأرض أو مفاتيح الأرض، وإني والله ما أخاف عليكم أن تشركوا بعدي، ولكن أخاف عليكم أن تتنافسوا فيها.
Bukhari narrated it in Maghazi (4042), and Muslim in Fadail (2296-30), both through the route of Yazid bin Abu Habib, from Abu Khayr, from Uqba bin Amir, who said, and then he mentioned it.His saying, "Indeed I am a forerunner for you," means, one who goes ahead of you. It is said, "The people went ahead," meaning they went ahead to the water.