The Messenger of Allah (peace and blessing of Allah be upon him) said: "Richness does not lie in the abundance of worldly goods but richness is the richness of the soul (heart, self)."

(Muslim)

(134) On the authority of Anas Bin Malik (may Allah be pleased with him) who said:

The Messenger of Allah (peace and blessing of Allah be upon him) said: "If there was one valley of gold for the son of Adam, he would long for another one. A man will never be satisfied, only death will stop him from being greedy. Allah returns to him who repents."

(Muslim)

Note: "Son of Adam" means fellow man. This because all of humanity is descended from Adam.

(135) On the authority of Abu Hurairah (may Allah be pleased with him) who said:

The Messenger of Allah (peace and blessing of Allah be upon him) said: "The heart of an old person is young for two things: for long life and love of wealth."

(Bukhari and Muslim)