dirty money

There is a story about a person wishing to give money to a yeshiva but the Rosh Yeshivah refused saying that he sensed that this was tainted money. It turned out that the potential donor confessed that he had stolen the stipend of the Vilner Gaon who said nothing about his lack of funds.
Since this money was gotten through the pain of another it could not be used for Tzedakkah.
In a similar vein our father Avrohom refused the payment for his fighting for the people of Sodom even though he had previously taken payment from Pharaoh
and later Avimelech for having embarrassed his wife, Sarah.Why take from one king and not a penny from another?
The ultimate answer is that the people of Sodom were unusually cruel and sadistic.
Most of their wealth was gotten through others' misfortune and the King was the worst perpetrator of that sadistic behavior. Accordingly Avrohom felt that the King's money was tainted with the suffering of others and he refused to take any benefit from such wealth.
In fact the wealth of Sodom had to be totally destroyed. For even Lot who was saved
could not take anything of value with him and if he did ,the benefit would doom him with the city.
Perhaps this is one of the many reasons that the Rebbe Z.T.L. refused to have any of his institutions get money through Bingo. Many a paycheck has evaporated at the tables of addicted bingo players. The Rebbe would forgo the benefit if it meant that another human being had suffered in granting that dollar!