Terumot, Chapter Three, Mishnah One
This mishnah deals with a person who gave something as terumah that seemed to be good when he gave it but turned out to be bad afterwards.
1) If one gave a cucumber as terumah and it was found to be bitter, a melon and it was found to be rotten, it is considered terumah, but he must again give terumah.
2) If one gave a jar of wine as terumah and it was found to be vinegar:
a) If prior to his act he knew that it was vinegar, the terumah is not valid;
b) But if it had turned sour after he had given it as terumah, behold it is terumah.
3) In case of doubt, it is terumah but he must again give terumah.
a) The first terumah does not render on its own [produce into which it falls] doubtful terumah and it is not subject to the added fifth, and so the second.
Section one: If one gave melons or cucumbers as terumah thinking that they were good and then it turned out that they were bad, the terumah counts, but he must again give terumah. The fact that this is terumah fits with that which we said in 2:6 (yesterdays mishnah) that if one gives terumah from bad produce for good produce his terumah counts. The new information here is that he must again give terumah. The Yerushalmi explains that bitter cucumbers and bad melons may not even count as food and hence it turns out that he may not have given any terumah whatsoever. Therefore, he must give terumah again.
Section two: If he gives wine as terumah, knowing that the wine has already turned into vinegar then the terumah doesnt count. The Yerushalmi explains that according to this mishnah holds that vinegar and wine are two different kinds, and as we learned above, when one tries to give one kind for another kind, his terumah is not valid. Had this been a case of giving bad for good his terumah should have counted.
However, if it turned into vinegar after he had already set it aside as terumah, then it is terumah, because when he made it into terumah, it was still wine.
Section three: If he doesnt know whether the wine was vinegar or wine when he declared it terumah, he must act stringently. The first terumah remains terumah and he must give again. If the first terumah fell into a pile of regular produce, it does not render the entire pile doubtful terumah because this terumah may not really be terumah (if it was vinegar before he gave it as terumah for the wine). Similarly, if the second terumah falls into a pile of regular produce, it doesnt render that pile into doubtful terumah because it too may not in actuality be terumah (if the first terumah was wine before he gave it as terumah, then the second terumah was unnecessary). Only if they fall in together do they cause the other produce into which they fall to become doubtful terumah.
Furthermore, a non-priest who eats either of the terumot is not liable to pay back an extra fifth, as is normally the case when a non-priest eats terumah. However, if he ate both terumot, he would have to pay the extra fifth because in such a case he certainly has eaten terumah.
For an explanation of a similar, yet somewhat different case, see above 1:8.