פועל משלו הוא אוכל (Bava Metzia 92a)

The Gemara says that the נ"מ is whether or not he can give to his wife and children. The Tur raises the question, what about if he picks it up to eat himself and then decides to give it to his wife or children (even if משמים הוא אוכל)? The Tur has 2 opinions and rejects the opinion that it is permitted. The Gra on Shulchan Aruch says that the 2 opinions are based on a machlokes Rashi and Tosafos. Rashi says "כל זמן דלא מטי לידיה לא זכי ליה". The implication is that once he does pick it up it his to do what he wants with including giving to his wife and kids. Tosafos however, says that he is not זוכה until he is "לועס ואוכל" which means that he cannot give it to his wife and kids.

In truth, Rashi on ד"ה אינו קוצץ) עמוד ב ) seems to say like Tosafos "דאין לפועל קטן זכות אלא שנותן לתוך פיו"

Also, in truth, Tosafos is a bit of a פלא, why should he only be זוכה when he puts it in his mouth? Why should this be different then any other מתנות עניים?

אתנן אסרה תורה (Bava Metzia 91a)

The way we have the גירסא the מסקנה is that there is no חיוב that ב"ד can impose because of קם ליה בדרבה מיניה however there is a חיוב בבא לצאת ידי שמים.

The מאירי in בבא קמא quotes a number of Rishonim who have a different גירסא in the Gemara and come to the opposite conclusion. They learn that both by אתנן and חסימה there is a חיוב to pay that ב"ד can enforce. What happened to קם ליה בדרבה מיניה? They learn that קם ליה בדרבה מיניה does not apply to a התחייבות מדעת. It only applies to a חיוב that is based on an action not a person's דעת. It comes out that according to these Rishonim by חסימה you would not say קם ליה בדרבה מיניה because the renter of the פרה agreed to the חיוב מדעת.

חסמה בקול (Bava Metzia 90b)

The simple understanding of the Gemara is like Rashi that he causes the animal not to eat by his voice by yelling at the animal when it is about to eat.

However, if you look carefully at Tosafos (ד"ה רבי יוחנן), you will see that Tosafos disagrees. Tosafos is bothered by a question that רבי יוחנן himself holds that עקימת שפתיו is not a מעשה by נשבע מימר ומקלל and therefore what is the חילוק here and why should חסימה בקול be חייב? Tosafos answers that here he is causing the animal to be דש with his voice and therefore בדיבוריה קא עביד מעשה. Tosafos learns pshat in חסמה בקול that he muzzled the animal normally and then with his voice caused the animal to be דש. This is very difficult in the words of the Gemara, according to Tosafos the Gemara should have asked דשה בקול. He wasn't חוסם בקול here at all. Tosafos is forced into this pshat because they need his דיבור to actually do something, cause the עבירה to happen. By לא תחסם the עיקר עבירה is the דישה while the animal is muzzled and therefore they had to learn that his דיבור caused the דישה.

when did Rabbi Shimon Bar Yochai die?

Yesterday we said in shiur, based on Rashi that R' Elazar's father Rabbi Shimon Bar Yochai had already died when they were young guys learning in front of Rashbag and Rav Yehoshua Ben Karcha. The Ben Yehoyada points out that this is difficult, since as we know, and we saw it today in shiur, he spent thirteen years in the cave learning with his father and the Ben Yehoyada insists that this story has to take place when R' Elazar was still young. Therefore he suggests that Rashbi was just not around but he was still alive

Who is עובר לפני עור when lending money בריבית? (Bava Metzia 75b)

The simple understanding of the Gemara is that לפני עור only applies to the מלוה and the לוה and that they are always עובר. Tosafos points out that the ערב and עדים can also be עובר if the loan would not take place without them.

The questions can be asked, why are the מלוה and the לוה always עובר? Let's take the following case. Reuven wants to lend money בריבית. Both Shimon and Levi want to borrow. Reuven decides to lend to Shimon. Why should Shimon be עובר לפני עור, after all, if Shimon didn't borrow the money Levi would have? Why isn't this a classic case of חד עברא דנהר where there is no לפני עור?

The ( משנה למלך (הל' מלוה ולוה ד:ב quotes the פני משה who says exactly this. If there were other borrowers available then there is no לפני עור on the לוה. However the משנה למלך disagrees and says the following סברה.

The only time there is a heter of חד עברא דנהר is when without you, the other person could do the עבירה with no help. In the classic case of נזיר, without you he could go and get the wine himself. Since he can violate the עבירה with no help from a Jew, your helping him does not violate לפני עור. However, by ריבית, the only way the מלוה can violate the עבירה is if a Jew helps him. The מלוה needs a Jewish לוה. Therefore, even if there is another Jewish לוה, since, bottom line, a Jew will be מכשיל him, there is an איסור of לפני עור. The fact that if Shimon won't borrow the money Levi will, is irrelevant, the bottom line is that for him to violate the עבירה he needs the help of a Jew (and מאי נפקא מינא whether it is Shimon or Levi, someone is being מכשיל him)and therefore there is always לפני עור by the לוה.

Is there a general היתר of כיכר? (Bava Metzia 75a)

Rashi understands ר' יהודה אמר שמואל that לוין סתם refers to ככרות and that the חכמים are מתיר in any case. However, the Rambam and the Rif learn that even ככר is only מותר if there is a שער and this is how the Shulchan Aruch paskens. The Rama is מתיר like Rashi that a דבר מועט like a loaf of bread is permitted in any case.

תלמידי חכמים מותרים ללות בריבית (Bava Metzia 75a)

Is it permitted for them to make this arrangement up front (פסיקה)?

The Rambam seems to say no. The Rambam is only מתיר a ת"ח to return more (without any pre-arangement at the time of the loan). The Gra learns that the Rambam is מדקדק from the fact that the Gemara said ללות and not להלוות. The obvious question is the המשך הגמרא. The Gemara brings the story of Shmuel where he seems to be פוםק beforehand that he will borrow 100 and return 120. The Gra explains that the Rambam understood that Shmuel was not being פוסק but rather was just raising the possibility that he might return more because he will not be מקפיד to count. The Shulchan Aruch paskens like the Rambama however, the Rama paskens that it is even מותר to be פוסק beforehand.