Laws of Robbery or Loss, chapter 14, law 6. Rav Shach asks a question on Tosphot in Bava Kama page 69a. According to Tosphot, a person that steals from a robber (after the owner has already given up on getting the object back), is liable to repay four or five. (A thief that steals a sheep is required to repay four sheep and if he stole an ox, he is required to repay 5 oxen). Rav Shach asks on this how is this possible. it has already gone out of the possession of the owner what Rav Shach intends to ask here is in a case where a robber has taken an animal and the owner has given up on getting it back. then a thief steals it from the robber. At that point there has been giving up and change of possession, and therefore the thief owns the animal. So, if he sells or slaughters the animal, he ought not be liable for 4 or 5. According to the Gemara on page 68 a, there the gemara holds that even though a thief is usually liable for four or five, however if he already owns the animal, he is not liable for that amount. After all, he is selling what already belongs to him or slaughtering what already belongs to him. The answer to this question I believe is found on page 68b in the second approach of the Gemara. There is an argument between R. Yochanan and Reish Lakish if a thief sells an animal after the owner has given up. Reish Lakish said he is not liable because he is selling what already belongs to him. R Yochanan disagrees with this logic and states that he is liable. So, we see that R. Yochanan does not hold with the reasoning of “he is selling what already belongs to him,” and therefore is not liable. So, we can answer the question of Rav Shach on Tosphot. Here, Tosphot is going like R. Yochanan and therefore even a thief of a robber after the owner has given up the thief is still liable to repay four or five. HOWEVER, ONE might ask on this because R Yochanan might disagree with Reish Lakish in the question of whether giving up alone causes acquisition. The way it seems at this point, is that he holds giving up alone causes acquisition, but even so, he does not think that is a preventative from bringing four or five. That is, he agrees he is selling his own property, but even so is required to bring four or five because he did steal the animal. But it is also possible to say that R Yochanan disagrees with Reish Lakish in this question, does giving up alone causes acquisition? Perhaps only giving up along with change of domain causes acquisition. In that case, the reason R. Yochanan holds him to be liable is that he is not selling an animal that belongs to him, but rather which belongs to the one stolen from. I WOULD LIKE TO ADD here as a side note that R Yochanan also holds that if the thief sells the animal before the owner has given up, he is also liable in four or five. At first, I thought the reason is that even though the sale is not valid, still the act o going through with the sale makes him liable. Later I saw that Rav Shach in laws of theft chapter 1 law 14 brings that a robber has certain rights in the object he stole before he gives it back, for example if he plows with the ox he stole he does not have to pay what profits he made from that. He only gives back the ox or pays back the value of the ox as it was worth at the time of the sale. So, in our case here R Yochanan holds the reason the thief pays four or five that the sale is valid to some degree even though he did not own the animal. (I am assuming here that a thief is like a robber in this aspect of also having certain rights in the object before it is given back.) It is valid to the degree that the buyer still ahs certain rights in the animal until it is given back to the rightful owner. ------------------------הלכות גזלה או אבדה פרק י''ד הלכה ו'. רב שך asks a question on תוספות in בבא קמא דף ס''ט ע''א. According to תוספות, a person that steals from a robber (after the owner has already given up on getting the object back), is liable to repay four or five. (A thief that steals a sheep is required to repay four sheep and if he stole an ox, he is required to repay 5 oxen). רב שך asks on this how is this possible. it has already gone out of the רשות of the owner. What רב שך intends to ask here is in a case where a גזלן has גזל an animal, and the owner has given up on getting it back. Then a גנב steals it from the גזלן. At that point there has been giving up and change of possession, and therefore the גנב owns the animal. So, if he sells or slaughters the animal, he ought not be liable for four or five. According to the גמרא on page ס''ח ע''א, that even though a גנב is usually liable for four or five, however if he already owns the animal, he is not liable for that amount. After all, he is selling what already belongs to him, or slaughtering what already belongs to him. The answer to this question I believe is found on page ס''ח ע''ב in the second approach of the גמרא. There is an argument between ר' יוחנן and ריש לקיש if a thief sells an animal after the owner has given up. ריש לקיש said he is not liable because he is selling what already belongs to him. ר' יוחנן disagrees with this logic, and states that he is liable. So, we see that ר' יוחנן does not hold with the reasoning of “he is selling what already belongs to him,” and therefore is not liable. So, we can answer the question of רב שך on תוספות. Here, תוספות is going like ר' יוחנן and therefore even a גנב of a גזלן after the owner has given up the thief is still liable to repay four or five. HOWEVER, ONE might ask on this because ר’ יוחנן might disagree with ריש לקיש in the question of whether יאוש כדי יאוש לבד בלי שינוי רשותcauses acquisition. The way it seems at this point, is that he holds יאוש כדי causes acquisition, but even so, he does not think that is a preventative from bringing four or five. That is, he agrees he is selling his own property, but even so is required to bring four or five because he did steal the animal. But it is also possible to say that ר’ יוחנן disagrees with ריש לקיש in this question, does יאוש כדי causes acquisition? Perhaps only ייאוש עם שינוי רשות causes acquisition. In that case, the reason ר’ יוחנן holds him to be liable is that he is not selling an animal that belongs to him, but rather which belongs to the one stolen from. I WOULD LIKE TO ADD here as a side note that ר' יוחנן also holds that if the thief sells the animal before the owner has given up, he is also liable in four or five. At first, I thought the reason is that even though the sale is not valid, still the act o going through with the sale makes him liable. Later I saw that רב שך in בהלכות גנבה פרק א' הלכה י''דbrings that a גזלן has certain rights in the object he stole before he gives it back, for example if he plows with the ox he stole he does not have to pay what profits he made from that. He only gives back the ox or pays back the value of the ox as it was worth at the time of the sale. So, in our case here ר' יוחנן holds the reason the thief pays four or five that the sale is valid to some degree even though he did not own the animal. (I am assuming here that a גנב is like a גזלן in this aspect of also having certain rights in the object before it is given back.) It is valid to the degree that the buyer still has certain rights in the animal until it is given back to the rightful owner.