The Mystery Of The Unidentifiable Kosher Esrog

A person has a collection of three esrogim, two of which are pasul [e.g. they are orlah] but he doesn't know which are the pasul ones. Then two of the esrogim separate from the mixture. Can he take the remaining esrog based on the rule of כל דפריש מרובא פריש  - anything that separated, we assume that it separated from the majority. Here too, we can say that the two esrogim came from the majority which were pasul and therefore the remaining esrog should be assumed kosher.

However, there is a very famous opinion of the חוות דעת that all mitzvos must be performed with complete certainty that the mitzva is being done properly. In this instance there is still a doubt as to whether the remaining esrog is kosher [assuming that רוב doesn't create a ודאי - which is the subject of much discussion]. If so, one would NOT be able to use it. There is also the opinion of the Nesivos who says that the דין of רוב is only for the part that separated but not on what remains. If so, the fact that two esrogim seperated from the רוב פסולים can tell us nothing about the esrog that remains. According to this, one would not be able to take the remaining esrog.

עיין באר שרים על המועדים סימן כה 

Maybe we have a simple solution - take all three!

This leads us to a very famous question - What is the din of a person who has two esrogim, one kosher and one orlah and pasul, may he take them BOTH and be יוצא because he knows he took a kosher esrog. Or maybe no, since both esrogim are forbidden to be eaten [because they both might be the pasul one] he may likewise not be יוצא with either [to be יוצא the esrog must be מותר באכילה].

I hope to get to that question. Lots of literature - not enough time:-).