Allah T'ala says in the Holy Quran:
قُل لاَّ يَسْتَوِي الْخَبِيثُ وَالطَّيِّبُ وَلَوْ أَعْجَبَكَ كَثْرَةُ الْخَبِيثِ فَاتَّقُواْ اللّهَ يَا أُوْلِي الأَلْبَابِ لَعَلَّكُمْ تُفْلِحُونَ
(5:100) (O Messenger!) Say to them: "The bad things and the good things are not equal, even though the abundance of the bad things might make you pleased with them. Men of understanding, beware of disobeying Allah; then maybe you will attain true success.'
This verse enunciates a standard of evaluation and judgement quite distinct from the standards employed by superficial people. For the latter, for instance, a hundred dollars are worth more than five dollars, since a hundred is more than five. But, according to this verse, if those hundred dollars have been earned in a manner entailing the disobedience of God the entire amount becomes unclean. If, on the contrary, a man earns five dollars while obeying God then this amount is clean; and anything which is unclean, whatever its quantity, cannot be worth that which is clean. A drop of perfume is more valuable than a heap of filth; a palmful of clean water is much more valuable than a huge cauldron brimming with urine. A truly wise person should therefore necessarily be content with whatever he acquires by clean, permissible means, however small and humble its quantity may be. He should not reach out for what is prohibited, however large in quantity and glittering in appearance.