Menahot, Chapter Twelve, Mishnah Four
1) A man may offer a minhah consisting of sixty tenths and bring them in one vessel.
2) If one said, I take upon myself to offer sixty-one tenths, he must bring sixty in one vessel and the one in another vessel, since the congregation brings on the first day of the festival [of Sukkot] when it falls on Shabbat sixty-one tenths [as a minhah], it is enough for an individual that [his minhah] should be one tenth less than that of the congregation.
3) Rabbi Shimon said: but some of these [sixty-one tenths] are for the bullocks and some for the lambs, and they may not be mixed one with the other! Rather sixty tenths mingles [in one vessel].
4) They said to him: can sixty be mingled [in one vessel] and not sixty-one?
5) He answered, so it is with all the measures prescribed by the sages: a man may immerse himself in forty seahs of water, but he may not immerse himself in forty seahs less one kortob.
6) One may not offer one [log], two, or five [logs], but one may offer three, four, six, or anything above six.
Section one: As we shall see in the argument below between Rabbi Shimon and the other sages, all agree that a person can voluntary bring a minhah of up to sixty tenths and put it all into one vessel. The rabbis will argue below as to why this is permissible.
Section two: However, if he offers to bring a minhah of sixty-one tenths, he must put sixty in one vessel and one in another vessel. The number sixty-one is the number of tenths that would have been brought when the first day of Sukkot falls on Shabbat. Fifty-seven would cover the bullocks (13 x 3 tenths), rams (2 x 2 tenths) and lambs (14 x 1 tenth) that the musaf (additional offering), required. Two more tenths are for the tamid (daily) offering and two more tenths are for the musaf of Shabbat. This brings the total to sixty-one. According to the first opinion, if an individual wishes to bring sixty-one tenths, he can only bring up to sixty in one vessel, such that he will have one less than the congregation brings.
Section three: Rabbi Shimon points out that these sixty-one tenths are not mixed in together on Sukkot, since they are for different animals. The reason that one can bring sixty tenths in one vessel has nothing to do with the amount brought on Sukkot. Rather sixty tenths of flour can mix with one log of oil, but sixty-one cannot.
Section four: The other rabbis question Rabbi Shimon. If sixty-tenths can mix in with one log of oil, then surely sixty-one tenths can also be mixed. Is one extra tenth really going to make that much of a difference!
Section five: Rabbi Shimon responds by simply noting that this is the way that halakhah works. When the rabbis set an arbitrary number, that arbitrary number is mandatory and even the smallest deviation is not accepted. For instance, a mikveh is valid if it has 40 seahs of water. If even the smallest amount, a kortov, is missing, the mikveh is invalid, even though such a small absence would not be at all noticeable. Thus, the rabbis have established that sixty seahs can be mixed in one vessel with one log of oil, but sixty-one cannot.
Section six: This section begins a new topic. One can voluntary offer three, four, six or more logs of wine, but not one, two or five, for these numbers are never found in the libation offerings mentioned in the Numbers 14:5-10. Three logs are for a lamb, four for a ram and six for a bullock (see also Menahot 9:3). Any number above six is a possible combination of 3, 4 and 6. For instance, 7 would be a lamb and a ram. Eight would be two rams, nine, three lambs and so on. Thus one can make a voluntary offering of wine consisting of any number higher than six logs.