It is said that Ka'b al-Ahbar was questioned about what is soundest and what is most corrupt in faith. 'The soundest thing is scrupulousness and the most corrupt is greed,' he replied.
Avarice is the wine of Satan, which he gives to his chosen ones with his own hand. Whoever becomes drunk upon it sobers up only in the pain of Allah's punishment in the proximity of the one who gave him the drink. If there were no other reason for Allah's wrath with respect to greed except man's preferring this world to faith, that would still be a sufficiently severe chastisement. Allah said,
أُوْلَـئِكَ الَّذِينَ اشْتَرُوُاْ الضَّلاَلَةَ بِالْهُدَى فَمَا رَبِحَت تِّجَارَتُهُمْ وَمَا كَانُواْ مُهْتَدِينَ
The Commander of the Faithful said, 'Be gracious to whoever you wish and you are his prince. Seek help from whoever you like and you are his equal. Be in need of whoever you like and you are his prisoner.' He who is greedy is stripped of his belief without feeling it, for belief prevents the bondsman from being greedy in creation. He also says, 'My friend, the vaults of Allah are full of marks of honour, and He does not neglect to reward of someone who acts well.'
Whatever a person might possess is tarnished by defects. Belief makes him rely on trust, moderation, forsaking desire, clinging to the obedience of Allah, and despairing of people. If he does that, then he is keeping close to his belief and he has acted correctly. If he does not, belief parts company with him and leaves him to his bad nature.