The book called "Torat Kohanim" [behukatai 12 perek 5] [which is from the sages of the Mishna but not included in the Mishna. Written around 160 A.D.] asks how do you know one the receives the second tithe as an inheritance can redeem it? Answer: הכתוב אומר גאול יגאל he will surely redeem it. [The extra word comes to include not just the owner but also one that inherits from him. ]
This has a difficulty in getting it to correspond to the Gemara in Zevachim pg 6.
The Raavad there explains that Braita in two ways. One way is that it is going according to "the second tithe is the money of the owner". The other is "the second tithe is the money of heaven"
The second way seems fine. But the first way --which works in its place does not seem to fit that Gemara. Rav Shach has an answer for this difficulty in Laws of Temura,
The Gemara in Zevachim says How do we know that one who inherits an animal that has been dedicated as a sacrifice can do Temura [An illegal exchange which nonetheless puts holiness on the second animal]? Because the verse says "he shall surely exchange". המיר ימיר. [And that should work for the second tithe also.] But in terms of temura, only one inheritor can make an exchange, not two. That is they are not partners in ownership. Rather they own as far as "forgiveness of sin" is concerned. That is: they bring the animal that their father or mother left to them as an inheritance But not as joint owners but as far as accomplishing the sacrifice.
This Gemara does not seem like the opinion of light sacrifices and or the second tithe are property of their owners, not of heaven.
Rav Shach says that is only in the very end of that Gemara does that conclusion arise, not in the middle discussion. But I can not see how even the end of that Gemara can be in accordance with "light sacrifices are the property of their owners."
Later I saw what Rav Shach says. It is this: the end part of that Gemara means that light sacrifices are the property of their owners means property as far as forgiveness for sin goes. Not monetary ownership. This answers my question completely.
So from the side of 'light sacrifices are the property of heaven" it all makes sense: one inheritor can do exchange because to do exchange one does not need to own the animal but rather to be the one that is receiving forgiveness for sin.[Just two inheritors are excluded by means of the verse.] And two inheritors can bring the flour offering because they do not own it at all. And maasar sheni they can do"hilul" make a valid exchange because of the verse that includes inheritors and it can not include them as owners because maasar sheni is the property of heaven, so it must include them as being able to make exchange.
But from the side of "light sacrifices are the property of the owners" the way I think Rav Shach is explain this is that the owners only own the animal in so far as forgiveness of sin is concerned. But maasar sheni comes out well. But what about the flour offering that can be brought only by one individua;? So I am still pondering what Rav Shach means here.
But in the meantime I just want to add a bit of info. the first tithe everyone knows about. You have a field of grain. You take 1/10 and give it to a Levi. The next tithe is in years 1,2,4,5 of the Sabatical cycle. That means to take the next 1/10 of what is left and take it to Jerusalem and eat it within the walls of the city.
But if that is too much to take there you can redeem it. You take a coin and say the holiness of these fruits and or grains of maasar sheni the second tithe is by this declaration now upon this coin. Then you take the coin to Jerusalem and there you buy fruit or grain and eat there. [That is called redeeming the second tithe maasar sheni][You can find this procedure in the Bible in the Book of Deuteronomy.]
