Sahih Bukhari Volume 4, Book 52, Hadith Number 95.
Narated By Abu Said Al-Khudri : Allah’s Apostle ascended the pulpit and said, “Nothing worries me as to what will happen to you after me, except the temptation of worldly blessings which will be conferred on you.” Then he mentioned the worldly pleasures. He started with the one (i.e. the blessings) and took up the other (i.e. the pleasures). A man got up saying, “O Allah’s Apostle! Can the good bring about evil?” The Prophet remained silent and we thought that he was being inspired divinely, so all the people kept silent with awe. Then the Prophet wiped the sweat off his face and asked, “Where is the present questioner?” “Do you think wealth is good?” he repeated thrice, adding, “No doubt, good produces nothing but good. Indeed it is like what grows on the banks of a stream which either kills or nearly kills the grazing animals because of gluttony except the vegetation-eating animal which eats till both its flanks are full (i.e. till it gets satisfied) and then stands in the sun and defecates and urinates and again starts grazing. This worldly property is sweet vegetation. How excellent the wealth of the Muslim is, if it is collected through legal means and is spent in Allah’s Cause and on orphans, poor people and travelers. But he who does not take it legally is like an eater who is never satisfied and his wealth will be a witness against him on the Day of Resurrection.”