Gemara

(Mishnah - R. Yehudah): If one (brought his olives to where we press them and) turned over his olives and he became an Avel or an Ones occurred or workers tricked him (and he was unable to press them before the Mo'ed), he may put the first beam on them and leave them for after the Mo'ed;

R. Yosi says, he may finish (pressing) and seal (the barrels of oil) normally.

12a (Mishnah - R. Yosi): If one had (new) wine in his winepress, and he became an Avel or an Ones occurred or he was tricked, he may finish and seal normally;

R. Yehudah says, he covers it with boards so it will not sour.

(Gemara): Both Mishnayos are needed:

If only the first Mishnah was taught, one might have thought that R. Yosi permits finishing only regarding oil, for it can incur a great loss, but he would agree with R. Yehudah about wine;

If only the second Mishnah was taught, one might have thought that R. Yehudah argues only about wine, but he agrees about oil (for it can incur a great loss).

(R. Yitzchak bar Aba): One who requires a Shinuy for Devar ha'Eved is unlike R. Yosi.

Question: May one seal a barrel of beer on Chol ha'Mo'ed?

Answer (Rav Nachman): Rav Yosef said that the Halachah follows R. Yosi (who permits).

Question: R. Yosi permits regarding wine. He did not (explicitly) permit regarding beer!

Answer: He permits regarding wine because it is a big loss. Also regarding beer it would be a loss!

(Abaye citing his surrogate mother): A sealed barrel filled with six Sa'im of beer is worth more than eight Sa'im in a big container.

(Rav): The laws of Chol ha'Mo'ed are like laws of Kusim.

(Rav Daniel bar Katina): This means that we cannot learn one from another:

Shmuel permits to be Zofes (line with pitch) a flask, but not a barrel. Rav Dimi of Neharda'a permits to be Zofes a barrel, but not a flask.

Rav Dimi allows only for a barrel, for it is a considerable loss (much seeps through if it is not lined). Shmuel forbids only a barrel, for it is a big exertion.

Rav Huna harvested on Chol ha'Mo'ed.

Question (Rabah bar Rav Huna - Beraisa): Devar ha'Eved is permitted on Chol ha'Mo'ed. What is not Devar ha'Eved is forbidden;

This refers to detached things. What is attached is forbidden even if it will be totally lost.

If one does not have what to eat, he may reap, make piles, thresh, winnow and do Borer, as long as he does not thresh with cows.

Answer (Rav Huna): That is an individual's opinion. The Halachah does not follow it:

(Beraisa - R. Yosi): If something detached will incur a partial loss, it is permitted (to do Melachah to prevent the loss);

If something attached will incur even a total loss, it is forbidden.

Question: If it is R. Yosi, even threshing with cows should be permitted, for R. Yosi does not require a Shinuy for Devar ha'Eved!

Answer: Threshing without cows is common; it is not a Shinuy. (One may not use cows because then the matter becomes well known.)

Rav harvested on Chol ha'Mo'ed. Shmuel was upset.

Suggestion: Shmuel holds like an individual (R. Yosi, who forbids everything attached)!

Rejection: No. Rav harvested wheat, which is not Devar ha'Eved. 21. Question: If so, why did he do it? 22. Answer: Rav had nothing to eat. 23. Shmuel was upset before he heard that Rav had nothing to eat. Alternatively, Shmuel holds that an important person should be more stringent.

Rishonim

Rif and Rosh (2:13,14): One may seal a barrel of beer on Chol ha'Mo'ed because the Halachah follows R. Yosi, and not sealing it would be a loss. We cannot learn laws of Chol ha'Mo'ed one from another. Shmuel permits to be Zofes a flask, but not a barrel, and Rav Dimi says oppositely. Rav Dimi requires a (sizable) loss; Shmuel forbids great exertion.

Hagahos Ashri: We may be Zofes our barrels. Since our wine is weak and spoils easily, it is a big loss, and even Shmuel permits. One with Yir'as Shamayim will do so before Yom Tov.

Rosh (14): The Heter to be Zofes a barrel is when he did not have time before the Mo'ed, or he thought that he can do so after the Mo'ed without a loss. But if he intended to do so during the Mo'ed, even Devar ha'Eved is forbidden.

Rif (according to Hagahos me'Eretz Yisrael): Rav harvested on Chol ha'Mo'ed. Shmuel was upset. Shmuel does not hold like an individual (R. Yosi, who forbids everything attached). Rather, Rav harvested wheat, which is not Devar ha'Eved. Shmuel had not heard that Rav had nothing to eat. Alternatively, Shmuel holds that an important person should be more stringent.

Rambam (Hilchos Yom Tov 7:2): If there will be a loss if a Melachah is not done, it is permitted on Chol ha'Mo'ed as long as it is not a big exertion.

Rambam (3): One may turn over his olives during the Mo'ed, grind and stomp them and fill barrels and seal them like on a Yom Chol.

Rebuttal (Ra'avad): The Gemara discusses one who already turned over his olives, for then it is Devar ha'Eved. A Beraisa says that this is only if he turned them over twice, but not if only once, for then they do not get so moldy (Yerushalmi 2:1).

Defense (Magid Mishnah): A Beraisa (11b) teaches that whatever one may do himself on Chol ha'Mo'ed, an Avel may ask others to do, such as olives to turn over. Further, since an Avel may ask others to turn over his olives, surely it is Devar ha'Eved. The Rambam holds that our Mishnah permits even though the olives were already turned and they will not get so moldy if left.

Ritva (11a DH Kach): Our texts here (and in Maseches Semachos 5:2) say 'if his olives were turned over'. If they were not turned yet, he can wait until after the Mo'ed. We must explain texts that say 'if he had olives to turn' to mean that he started and if he does not finish now, it will be a loss.

Drishah (OC 538:1): Why didn't the Rambam teach that it is permitted if the olives were already turned? We must say that there is a Chidush in each case, i.e. one might have thought that it is not a big loss, and the Rambam taught one of them.

Rambam (ibid.): Anything that entails a loss if not done normally may be done normally without a Shinuy.

Rambam (8:14): We may be Zofes barrels in order that the wine will not spoil. We may be Zofes a flask, for it is not an exertion. One may seal a barrel of beer so it will not spoil.

Magid Mishnah: We are lenient like both opinions

Rosh (15): If one's neighbors harvest their vineyards at the harvest time, it would be a loss not to harvest, lest the fence be breached and his vineyard be trampled. One may harvest and stomp the grapes and put the wine in barrels. If a Nochri wants to pay his debt with wine one may take it (lest the Nochri later refuse to pay). If one needs to buy wine for the entire year and it will not be available later like it is at the time of the harvest, this is Devar ha'Eved and it is permitted.

Poskim

Shulchan Aruch (OC 537:1,2): One may do Devar ha'Eved on Chol ha'Mo'ed without a Shinuy.

Shulchan Aruch (538:1): If one turned over his olives or had wine in his pit and an Ones occurred, or he forgot (to barrel them) or was sloth because he thought that it can wait until after the Regel, since it is Devar ha'Eved he may pour them into barrels and be Zofes them, whether they are big or small, and seal them normally.

Beis Yosef (DH u'Mah she'Chosav Rabeinu): The Tur assumes that the Rosh permits big and small barrels because he permits to buy wine for the year and to fix barrels and seal them with pitch, and he did not specify the size of the barrels. This is not a proof. 'Chaviyos' connotes big barrels. Perhaps we may infer that he permits big and small barrels from the fact that he brought both opinions. We are lenient about a Safek mid'Rabanan.

Question (Magen Avraham 1 and Gra DH Bein): In Siman 504, the Beis Yosef cited the Rosh who is stringent about a Safek mid'Rabanan (why we are more lenient about grinding spices than salt on Yom Tov). It is difficult to distinguish these. Also, the Gemara (Pesachim 108a) concludes that since we are unsure for which of the four cups on Pesach we must recline, we must recline for all of them.

Beis Yosef (DH u'Mah she'Chosav she'Yesh): The Tur brings an opinion that permits only big barrels, like Rav Dimi of Neharda'a. This is difficult, for Shmuel is cited more often in the Gemara.

Beis Yosef (DH Kosav b'Mordechai): The Mordechai says that the Gemara discusses putting pitch on the inside of finished barrels, to enable them to hold wine or beer.

Rema: Similarly, one may fix barrels by tying them with ropes. If one knows that he will need them during the Mo'ed he must do so beforehand.

Source (Beis Yosef citing Hagahos Maimoniyos): Surely fixing the wheel and cracks is Devar ha'Eved and is permitted. One must fix and tie the barrels before Yom Tov if he knows that he will need them.