One of the daily sacrifices brought by the High Priest was a griddle-cake offering called the minḥat ḥavitin. It consisted of loaves that were baked from a measure of flour, half of which were sacrificed on the altar in the morning and the other half which were sacrificed in the afternoon (see Vayikra 6:12-18).
According to the Mishna on today’s daf if the kohen gadol passed away after the morning minḥat ḥavitin had been brought, and no one had been appointed to replace him, Rabbi Shimon rules that the afternoon offering would be brought from the public coffers; Rabbi Yehuda requires those who inherit the kohen gadol to pay for it.
Although the source for these two opinions are based on Biblical passages, the Gemara points out that we find a baraita that lists this law among several that Rabbi Shimon identified as being Rabbinic ordinances. By way of explanation, Rabbi Abbahu suggests that there were two separate enactments. As the Gemara originally suggested, Rabbi Shimon believes that the afternoon offering should be brought from the public coffers. When public funding ran short the Rabbis ruled that those who inherit the kohen gadol are obligated to bring the offering. When it became clear that those people were unreliable, the law reverted to the original Biblical requirement.
The Ḥazon Ish points out that the original Rabbinic ordinance was problematic since a minḥat ḥavitin could not be brought as a voluntary donation. Since in this case the offerings really should have been brought from communal funds, how could private funds be used? He suggests that the way the ordinance was developed must have required the heirs of the kohen gadol to donate the money to the public coffers for the purpose of the public minḥat ḥavitin offering.