Rabbi Landau first discusses what the law would be in a case where the extra money wasn’t tzedakah. If it wasn’t tzedakah, the gabbai must only reimburse the amount he is sure is above and beyond what was in his purse originally.
In this case, though, Rabbi Landau rules as follows: The messenger, he writes, was errant and did not properly fulfill his mission, and we have a rule that (Bava Kamma 3b) “adam mu’ad l’olam – man is always considered warned.” He thus is responsible for any damage resulting from his negligent actions. Therefore, Rabbi Landau rules that the gabbai who sent the messenger is considered a watchman (shomer) who sent another watchmen, and the halacha is that such a shomer is responsible for the negligence of the second shomer (Bava Metzia 36b).
Therefore, the gabbai, in order to satisfy his heavenly obligation, must conduct a thorough study and analysis of his ledger over several years and determine the usual monthly donation of the donor. Following this, he must give to charity the sum that matches the highest monthly donation he finds. In so doing, he will go above and beyond the law and satisfy his heavenly obligation, for one is not required to take into account unusual occurrences; in other words, he needn’t worry that perhaps the person gave a larger monthly donation than he ever had previously.
(To be continued)