“I am your predecessor before you, and I am a witness upon you, and I am looking at my Tank just now, and I have been given the keys of the treasures of the world (or the keys of the world). By Allah, I am not afraid that you will worship others besides Allah after me, but I am afraid that you will compete with each other for (the pleasures of) this world.“ [Sahih Bukhari, Volume 5, Book 59, Number 411]