Menahot, Chapter Thirteen, Mishnah Five
Todays mishnah deals with one who has volunteered to bring wine or oil.
1) [If one said,] I take upon myself to bring wine, he must bring not less than three logs.
2) Oil, he must bring not less than one log;
3) Rabbi says: not less than three logs.
4) [If one said,] I specified [how much I would offer] but I do not know how much I specified, he must bring that quantity which is the most that is brought on any one day.
Section one: If he volunteered to bring wine, he must bring at least three logs of wine, which is the minimum amount of any of the libation offerings that accompany animal sacrifices (see above 12:4).
Section two: There is a debate about one who volunteers to bring oil. According to the first opinion, he must bring at least one log because an unspecified minhah is one tenth of fine flour (see 12:3), which requires one log of oil (see 9:3).
However, Rabbi [Judah Hanasi] says that he must bring three logs of oil, for that is the minimum amount of oil used in any of the libation offerings that accompany animal sacrifices (see 12:4). In other words, the first opinion holds that he might have referred to the oil that accompanies a minhah which is only a log, whereas Rabbi holds that we must be concerned lest he was volunteering the amount of oil that accompanies an animal sacrifice, which is three logs.