My neighbor who was going away for Pessach left me a box of chametz that he asked me to burn for him. The day before Erev Pessach I looked at the box and saw that besides cookies and bread, the box contained various bottles of vitamins that I also used and were worth a few hundred dollars. I figured that since I sell chametz anyway I could take the vitamins and they would be included in my sale of chametz since they would be mine at the time the rabbi sold my chametz and after Pessach when the rabbi buys back the chametz I would have free bottles of vitamins. All the vitamins were certified as kosher for non-Passover use by a reputable kashrus organization. After Pessach, I called the kashrus organization and asked if the vitamins were actually chametz and they told me that all save one were not chametz but since they were made with corn derivatives they cannot certify them as kosher for Passover use since Ashkenazim do not eat kitniyos on Pessach. My question is two-fold. Firstly, were my thoughts correct that since he wanted to burn his chametz I could take his chametz and so I can keep the bottle that is real chametz. Secondly, concerning the bottles that are only kitniyos may I keep them because one does not need to dispose of kitniyos since while Ashkenazim do not eat kitniyos on Pessach they may own them. Therefore, his desire to burn them was a total error. Perhaps, even if I may keep the chametz bottle I would have to return the rest of the bottles because it was a mistake on his part?
In order to answer your question we have to evaluate the legal status of the items your neighbor asked you to burn.
By telling you to burn these items your neighbor made a clear statement that he was no longer interested in using the contents of the box and did not expect them back. While he probably did not want to relinquish ownership on the entire contents of the box since the Ramo (OC 434, 2) rules that one should not declare, all of his chametz, ownerless (bitul chametz) before he burns his chametz since otherwise he will not be able to fulfill the minhag to burn his chametz, nevertheless it suffices to fulfill this minhag by burning one kezayis-a minimal amount of chametz. Therefore, it is quite certain that your neighbor would not mind if someone would take some of the items that were found in the box. This is even more certain in case someone could really use those items since it is midas sedom-Sodomite behavior for one to prevent others from using something that he himself does not need. Thus, we can safely assume that if anyone would have asked your neighbor for permission to consume some of his vitamins on Erev Pessach your neighbor would have granted him permission. Even more so this is true if you, his neighbor who was dong him the favor of ridding his chametz on his behalf, would have wanted to partake of his chametz.
We find in the Gemara and Shulchan Aruch various rulings concerning situations where an owner does not mind others taking his possession and from them we can derive the legal classification of the contents of the box. For example, the Gemara (Pessachim 6B) says that one who checked his house for chametz does not need to be concerned that perhaps he overlooked a few crumbs because even if he did overlook them, these crumbs are considered ownerless, even if they are inside his house, since the owner is not interested in them.
Even where an item is of value to people but the owner does not mind if someone takes it we find that one is allowed to take the item. Thus, the Shulchan Aruch (CM 359, 1), based on the Yerushalmi, rules that one may break off a thin branch from another person’s bush in order to clean his teeth since people don’t mind. It just says that it is a midas chassidus not to do so because (See Sema note 4) otherwise everyone will break off a little bit and the owner will eventually be harmed.
Another ruling concerning an object, whose owner doesn’t mind if someone took it, concerns betrothing a wife. Even though one must give his bride something that he owns, the Rambam and Shulchan Aruch (EH 28, 17) rule that if someone took, without permission, an object like one or two dates from someone that we surmise doesn’t mind that he took it, and gave it to his bride in order to betroth her it is a sofeik– a possibility that perhaps she is betrothed. The meforshim are divided why we are not certain that she is betrothed. Some (Presho) understand that it is because the object that he gave was worth less than a peruto-the minimum amount one needs to give his bride while others (Beis Shmuel) understand that it is because we aren’t certain that the owner truly does not mind. In your situation, we have no reason to be concerned with these issues because it is not important how much the vitamins are worth and you can be quite certain that your neighbor would let you keep it. The Acharonim also have various opinions if the dates were ownerless-hefkeir (Teshuvo Me’ahavo 3, 440) before the groom took them or there was just ye’ush-the owner lost hope that they would be returned (Noda Behehudo EH 2, 77).
Your situation is far better than the dates because we can 1-safely assume that your neighbor did not mind if someone would take some of the items in the box and 2-he expressed clearly that he did not want them returned-meaning that there certainly was ye’ush on his part.
We should note that certain conditions must be fulfilled in order for ye’ush to affect change of ownership. One condition is that that the object may not be in the possession of its owner or even someone who is a shomeir-guardian on his behalf. In your situation this condition was satisfied since the box was not in its owner’s possession and since you were given the objects in order to destroy them, the Gemara (BK 93A) states that you never assumed the status of a shomeir. As a result, your neighbor’s ye’ush was legally effective since it was neither in his hands nor in the hands of his legal shomeir. The other condition that is crucial for ye’ush to be legally effective is that it should have entered the possession of the one who wishes to keep it in a permissible manner. For example, a thief does not acquire an object that he stole even after the owner gave up hope of recovering his stolen property since it entered the possession of the thief in a prohibited manner. However, one who finds a lost object after the loser abandoned hope of having it returned may keep the lost object because it entered his possession in a permitted manner. In your case since it entered your possession in a permitted manner as we saw earlier, you may keep the items that your neighbor abandoned hope of having them returned. Therefore, we have established that your neighbor’s ye’ush enabled you to take possession of his vitamins. Furthermore, perhaps they were even hefkeir which would certainly allow you to keep his vitamins.
Based on the above, we can answer your question concerning the bottle that was chametz. You may certainly keep it since your neighbor wanted to get rid of his chametz and this bottle contained real chametz.
However, concerning the bottles that did not contain chametz, your neighbor’s desire to burn them was based on a mistake. Generally, when one acts based on a mistake his action is not legally effective because in order for an action to be legally effective the parties have to intend for it to be effective and intent based on a mistake is not intention. For example, when one purchases an item based on false premises the buyer may render the acquisition null and void-a mekach to’us because the buyer never intended to buy the object in its actual state.
Since we saw that the means by which you are able to acquire your neighbor’s vitamins are either hefkeir or ye’ush, where each one suffices, we have to investigate whether either hefkeir or ye’ush that is based on an error is legally effective.
Concerning hefkeir there are various sources that if the owner’s declaration that an item is hefkeir is based on a mistaken assumption the item is not legally hefkeir. For example, Tosafos (Gittin 47A) and the Rash (Peah 6, 1) explain that the reason the Gemara rules that if a gentile picks up a Jew’s forgotten grain-shikcho it is not his, is because the only reason the Jewish owner of the field rendered the forgotten grain as hefkeir is because he thought it would be picked up by a Jew. Since this turned out to be a mistake of judgment, the hefkeir was not effective.
Even where the mistake was not in circumstances but a legal error, Tosafos (Pessachim 57A) writes that the declaration of hefkeir is void. The case in the Gemara from which this is derived is where an owner of a vegetable patch left over peah-an act of hefkeir, which is unnecessary according to the halachah, and the Gemara ruled that the peah was not hefkeir because it was based on a mistake. Thus, if we would need to resort to hefkeir in order for you to acquire your neighbor’s non-chametz vitamins, you would need to return them to your neighbor.
However, we saw earlier that your neighbor’s ye’ush-lack of expectation that he would have the vitamins returned, suffices for you in order to acquire his vitamins. Therefore, we have to determine if perhaps ye’ush that is based on an error is valid.
The Gemara (Kresus 24A) rules that if witnesses testified that a person’s animal needed to be killed because an aveiro was done with it and later those witness’s testimony was declared invalid, nevertheless one who took possession of the animal in the interim may keep the animal even after the testimony was nullified. Many Acharonim explain that the reason the new owner may keep it is because the animal’s owner gave up hope of keeping his animal when beis din first ruled that the animal needed to be killed. Thus we see that even though the owner’s loss of hope was based on an error, nevertheless the ye’ush is valid. Thus we see that, in contrast to hefkeir, ye’ush that is based on an error is, nonetheless, legally effective. This is explicitly written by the Ketsos (siman 142) in a different context. The Ketsos proves his contention with the argument that the Gemoro states that when one gives up hope of recovering his lost object-ye’ush the finder may keep the lost object even though the only reason the owner gave up hope is because he didn’t know where his lost object was. Thus, ye’ush that is based on an error is legally valid. The rationale for the difference between ye’ush and hefkeir is that hefkeir is a positive action-to render the object ownerless whereas ye’ush is negative-loss of hope and one does not require as much desire to affect change in a negative manner-loss of hope in this case, as he does to affect change in a positive manner.
Returning to your second question-since in order for you to keep the vitamins ye’ush is sufficient and we have seen that ye’ush that is based on an error is effective, you may even keep the vitamins that are not chametz and you need not even inform your neighbor that you kept his vitamins.