The Talmud tells us that before reciting Grace After Meals, hands must be clean and fragrant (B. Brachot 53b). Hands that are dirty or that reek render the person unfit to recite Grace. According to one sage, just like an offensive odor disqualifies a person from doing Temple service, hands that have an offensive odor disqualify the person from reciting Grace After Meals. The requirement to wash hands at the end of the meal is called mayim aharonim (last water) and is codified as Jewish law (Shulhan Aruch OH 181:1). While there are authoritative medieval sources that explain the custom of those who do not wash their hands before Grace (Tosafot, 12th-14th centuries, France-Germany), mayim aharonim is nevertheless practiced by many. One of the most fascinating aspects of mayim aharonim is the lack of clarity surrounding the reason for the custom. From various talmudic statements, we can identify three possible reasons for this requirement (B. Hullin 105a-b). At first glance, mayim aharonim aims at cleansing the hands from food residue accumulated while eating. Following this approach, the Talmud tells us that only cold water should be used for mayim aharonim, since washing with hot water may soften the hands and result in the dirt being further absorbed rather than being washed away. Our sages further note that the obligatory nature of mayim aharonim stems from the fear of Sodomite salt that has the power to blind if it comes in contact with the eyes. While the precise identity and nature of Sodomite salt may be unclear to us today, it would appear that washing mayim aharonim serves to rid the diner - or indeed anyone who comes in contact with Sodomite salt - of any traces of this potent substance. Our sages also note that mayim aharonim should not be poured onto the floor, apparently because water used to clean dirty hands becomes vile and repulsive, and may even give off a foul odor (Rashi, 11th century, France). It appears, however, that the disquiet was not merely one of propriety and practicality; mystical concerns were also considered: Water used for mayim aharonim is considered to have an evil spirit resting upon it. Thus the used mayim aharonim should not be poured onto the ground, lest a passerby tread on these mystically sullied waters. This brings us to the second reason for mayim aharonim: to combat the mystical dirt associated with evil spirits. Then we come to the third explanation. Rav Dimi returned to Babylonia after visiting the Land of Israel, and upon his return he recounted laws, opinions and discussions he had witnessed or received while in the West. Among his reports, Rav Dimi related that because of a person's failure to wash mayim aharonim, he ended up divorcing his wife. Another rabbinic traveler who transmitted traditions from the Land of Israel to Babylonia - Ravin - related a similar tradition: Because of a person's failure to wash mayim aharonim, murder was committed (B. Hullin 106a). The connection between washing mayim aharonim on one hand, and a happy marriage or not committing a felony on the other hand, is unexplained by Rav Dimi and Ravin. However, the tale is told elsewhere in the Talmud (B. Yoma 83b). Three scholars - Rabbi Meir, Rabbi Yehuda and Rabbi Yose stayed at a certain inn one weekend. Before the onset of Shabbat two of the party - Rabbis Yehuda and Yose - deposited their money purses with Kidor the innkeeper for safekeeping. When they came to retrieve their money after Shabbat, Kidor denied ever being entrusted with the purses. The sages persuaded Kidor to join them for a drink, hoping that the alcohol would make him talk and he would reveal where he had stowed their money (Maharsha, 16th-17th centuries, Poland). The sages noticed that there were lentils on Kidor's mustache, and they hurried to Kidor's home to talk to his wife. When they met her, they said: "Your husband said that you should return our purses, and so you know we are telling the truth, he told us to mention that the two of you ate lentils today." The ploy worked: Indeed, the couple had eaten lentils, and based on this proof Kidor's wife returned the money purses. When Kidor discovered what had transpired, he was enraged. According to one version, he killed his wife; according to another version, he promptly divorced her. Had Kidor washed mayim aharonim, he presumably would have wiped his mustache, as people do, and his relationship with his wife would not have been harmed. Thus mayim aharonim is a remnant of a frightening historical episode, and while the codes do not mention the need to wipe your mustache as part of mayim aharonim, it is common practice to do so. One early codifier states that while the harmful Sodomite salt may no longer be part of our diet, this tale nevertheless indicates the continuing need for mayim aharonim (Rif, 11th century, North Africa). The sum of the talmudic mayim aharonim passages is a gamut of reasons: hygienic, mystical and commemorative. The different reasons reflect the attempt by our sages to find meaning in a prevalent practice with hazy origins. In this sense, mayim aharonim may be paradigmatic: Whenever we are faced with an established practice of our tradition, our first course should be to try to understand that practice. As can be expected, different people will connect to different themes: People raised with good manners and decency may understand that hand washing at the end of the meal is necessary to remove dirt; mystically minded people will seek the esoteric meaning behind the practice; and those with a keen sense of history and commemoration will recall events of the past that justify the practice in the present. Beyond the actual practice of hand-washing, the mayim aharonim discussion suggests a model for approaching our time-honored traditions: Even when the original motive has been lost, we are charged with seeking the tradition's relevance in our lives. The writer is on the faculty of Pardes Institute of Jewish Studies and is a rabbi in Tzur Hadassah.