Likutei Moharan 69:8/ליקוטי מוהר"ן ס״ט:ח׳

18. And know, by giving charity a person can rectify the ill-gotten money he has in his possession—i.e., that which he robbed by coveting. Only returning that which was robbed can remedy actual robbing. Likewise, if one has robbed from the community, he must use the ill-gotten money for the public good (Beitzah 29a). But if he possesses money robbed by coveting, he can rectify it through charity. Giving tzedakah (charity) causes it to remain as it is: his money remains his, even though it is [money] robbed through coveting.

2This is “He will sit smelting and purifying silver; he will purify the descendants of Levi and refine them like gold and silver, so that they will be for God presenters of offerings in tzedakah (righteousness)” (Malachi 3:3) . Concerning this verse, our Sages, of blessed memory, taught: God will be charitable, so that a family that has blended [into the Jewish people] beyond recognition shall remain that way (Kiddushin 71a) .

3In other words, through charity it is possible to remedy the theft, which is the same aspect as a family that has blended beyond recognition. Since he robs the souls of his neighbor’s sons and daughters and takes his wife, as explained above, it is therefore an intermingled family. But charity rectifies this: it remains as it is, as they said, “a family that has blended beyond recognition shall remain that way.” This is “He will sit as a refiner and purifier of silver… refining them like gold and silver”—he will purge and refine the robbed silver and gold, which corresponds to the family that has blended beyond recognition.