Rabbi Aryeh Leib Breslau (also known as Levij Heiman van Breslau; 1741-1809), Chief Rabbi of Rotterdam, has an interesting question in his Pne Aryeh (#41). It apparently concerns the Revolutionary War financier that all Jewish kids know about, Haym Solomon (הנדיב הרר"ח שבפילידעלפיא).
A prominent Dutch Jew named Gumpel Wolfenbütel asked Rabbi Aryeh Leib about a charitable donation he received from Haym Solomon, to be given to a specific needy person. Subsequently the person's fortune changed and the charity was no longer needed. The question was, is Wolfenbüttel obligated to give the money to the individual? Or perhaps he should return the money to Solomon, so that he will be inclined to give in the future?
(He finds that according to halacha once the money was pledged, let alone sent, it is already a binding transfer and thus already given. to change that would be like breaking a vow. Thus Solomon has no claim to it - not that he was asking for its return. The man should be given the money, but since he is not in need of charity then he should dispose of it in a charitable way.)
Here is the title page of the Pnei Aryeh:
Here are two images of Rabbi Aryeh Leib; one artist was kinder than the other: