From Sahih Bukhari (Hadith 3596):
Narrated `Uqba bin `Amr:The Prophet (ﷺ) once came out and offered the funeral prayer for the martyrs of Uhud, and proceeded to the pulpit and said, "I shall be your predecessor and a witness on you, and I am really looking at my sacred Fount now, and no doubt, I have been given the keys of the treasures of the world. By Allah, I am not afraid that you will worship others along with Allah, but I am afraid that you will envy and fight one another for worldly fortunes
Reference: Bukhari 3596