Halakhah sa Mga Bilang 32:22: Chafetz Chaim, Mishneh Torah, Gifts to the Poor, Gray Matter III & Shulchan Arukh, Choshen Mishpat

And even if he heard that Ploni caused him the loss, still, he is permitted only to suspect, but not to confirm it within himself as being true. And even if people stirred up a quarrel with the suspect, telling him that he had done a great wrong in what was heard of him, that he had caused a loss to a Jew — and he kept quiet, still, it is not to be concluded because of this that the thing is true. For though it is a mitzvah for him to rescue himself from suspicion and to convince the one who suspected him that he is not to be suspected, as per (Bamidbar 32:22): "And you shall be clean of [guilt against] the L–rd and [against] Israel," still, it may be that he saw them to be so entrenched in their acceptance of the slander as being true, that they would accept no answer from him, wherefore he decided that it would be best for him to remain silent and to be one of those "who are shamed, but do not shame [in return], who hear their disgrace and do not answer."

If a tzedakah collector engages in business with another in the market [while he is collecting tzedakah] and he [the other person] pays him [the collector in front of others], he may not place [the money] in his pocket, but rather he puts it in the money bag of tzedakah, and when he gets home he may take it out. He may also not count the money from the kupah two by two but rather one coin at a time so that there is no suspicion, as it is said, (Num. 32:22) You shall be clear before the LORD and before Israel.

The second partner complained to Rav Papa that he seemed to always side with the first partner. Rav Papa responded, according to Tosafot’s first interpretation, that in such a situation one must present a reason for his decision, which Rav Papa proceeded to give. Tosafot explain that in such a situation, in which there is a basis for a litigant to suspect the beit din of bias, the beit din should reveal its logic in order to “be clean in the eyes of Hashem and Israel” (Bemidbar 32:22). The Sema (14:23) clarifies, though, that this applies only if there is a reasonable basis for the charge of bias, as there was in Rav Papa’s case.²A second opinion in Tosafot, however, does not interpret Rav Papa in a manner that requires a beit din to clarify its grounds in such a case.