Shalom Philip,

Great to hear from you!

I often feel it's a good idea for me to check exactly to which passages you are referring. Because what I see at the moment is the following.

A. Bava Basra 8b.

Near the end of the Daf, the Gemara brings a Baraisa which teaches us that the Gabai Tzedakah may exchange copper charity coins for silver -- to avoid rusting -- if there are currently no needy people to whom he can distribute the funds. Similarly, the food supply from the Tamchuy can be sold if at the moment there are no needy people to eat it.

But I don't believe you could be referring to this passage, because in these cases we do not see that the Gabai can redistribute Tzedakah funds; on the contrary, we see that Tzedakah funds must be kept in reserve for eventual use, i.e. when new needy people eventually show up.

B. Arachin 6a-b

We see that Tzedakah which has already been donated and is in the hands of the Gabai, may generally speaking not be used for other purposes; but we learn from the story of Rebbe Yanai that this is flexible, and thus if taking from those funds (e.g. he borrowed them for his own personal needs - Rashi 6b DH Rebbe Yanai) will actually promote the donation of more charity, then that is permissible.

The same Daf teaches us that a donation to a Shul (not charity to the poor), e.g. a lamp, may not be used for purposes of Reshus, but it may be used for purposes of a Mitzvah, provided the donor was a Jew, or even if the donor was a gentile as long as people have forgotten that he is the one who donated it.

In Megilah 27a, I see a discussion not of Tzedakah, but of Tashmishei Kedushah (different than Tashmishei Mitzvah). There we learn that holy articles may be used for greater sanctified purposes, but not for lesser.

So at the moment I don't see a conflict between all the sources. But I will be happy to continue the conversation if there is a point you wish to clarify or add. Thank you!

May you continue to attain greatness in Torah and Yiras Shamayim!

Warmly,

Yishai Rasowsky