Abu Sa' eed Al-Khudri said: "The Messenger of Allah P.B.U.H stood up and addressed the people, saying: 'No by Allah I do not fear for you, 0 people, but I fear the the attractions of this world that Allah brings forth for you.' A man said to him: '0 Messenger of Allah, does good bring forth evil?' The Messenger of Allah remained silent for a while, then he said: 'What did you say?' He said: 'I said, does good bring forth evil?' The Messenger of Allah said: 'Good does not bring forth anything but good, but is it really good? Everything that grows on the banks of a stream may either kill if overeaten or at least) make the animals sick, except if an animal eats its fill of Khadir and then faces the sun, and then defecates and urinates, chews the cud and then returns to graze again. Whoever takes wealth in a lawful manner, it will be blessed for him, but whoever takes it in an unlawful manner, his likeness is that of one who eats and is never satisfied.''' (Sahih)