The last Mishna in our perek opens with a discussion of what to do if an animal is found in the environs of Jerusalem. We assume that it must be a korban; depending on its gender, it will either be brought as an ola or as a shelamim. The Mishna also describes how at first the person who found the animal was responsible to pay for the minhat nesakhim that went with it (flour and oil, as well as a wine libation). When people realized that bringing the lost animal to the Temple would be an expensive proposition for them, they would ignore such animals, so a court decision was made putting the responsibility for the minhat nesakhim on the community. Rabbi Shimon lists this as one of the seven takanot (remedy, ordinance) that the beit din made in connection with the Temple service.
…And the sixth ordinance concerned the red heifer: that deriving benefit from its ashes is not considered misusing consecrated property.
The para aduma was used during Temple times to purify people who had become ritually defiled through contact with a dead body. According to the Torah (Bamidbar 19:1-22), the para aduma is slaughtered and burned; its ashes are mixed with well-water (mayim hayyim) and that mixture is sprinkled on the person who is tameh. After a week has passed, the person goes to the mikveh and becomes tahor (ritually pure) once again.
For all that preparation of the para aduma is incumbent on the kohanim and is part of the Temple service, the para aduma is not considered a korban, as it is not slaughtered in the precincts of the Mikdash, but on Har ha-Zeitim, the Mount of Olives. As such, the holiness that it has is kodshei bedek ha-bayit, as something that belongs to the Temple treasury, rather than having inherent holiness.
According to the Gemara, me’ila (misusing consecrated property) can only take place if someone makes use of the para aduma itself. Me’ila cannot be done on the ashes of the para aduma. When the courts saw that the kohanim were using the ashes for medicinal purposes, they ruled that me’ila should apply to the ashes, as well. When it became clear that this new rule discouraged kohanim from participating in the ceremony where the para aduma water was used for its intended purpose, because they were afraid that they might accidentally derive benefit from it, the beit din returned the law to its original status, ruling that no me’ila applies to the ashes.