As we learned on yesterday’s daf, the Torah forbids using tainted money in the Temple. Thus, neither an animal given as payment to a prostitute for her services (etnan zona), nor money paid for purchase of a dog (mekhir kelev) can be used to bring a sacrifice in the Temple, as the Torah writes: “You shall not bring the payment of a prostitute, or the price of a dog, into the house of the Lord your God for any vow; for even both these are an abomination unto the Lord your God” (Sefer Devarim 23:19).
The Mishna on today’s daf clarifies that the prohibition applies not only to animal sacrifices, but to other sacrificial contributions, as well. Thus, if someone paid for the services of a prostitute with wine, oil or fine flour – all of which are used directly in the sacrificial service – those objects cannot be used in the Temple. If, however, payment was made in money, that money could be used to purchase sacrifices.
One exception to the above rule is when payment was made using something that was already consecrated for sacrifice. The Mishna teaches that such a thing remains permitted to be brought on the altar. Since an already consecrated object no longer belongs to its original owner, he does not have the ability to affect it in any way. The Mishna emphasizes that these rules include birds as well.
While Rashi understands that the statement about birds means that the rule remains the same for them so that an ordinary bird would be forbidden for sacrifice if it was used for improper payments but an already consecrated bird would be permitted, the Rambam rules that birds are an exception and that even a consecrated bird would be forbidden on the altar if it was used in this manner. This Rambam does not appear to agree with the simple reading of our Mishna, and many argue that he had a variant reading of the text. In his Even HaAzel, Rav Isser Zalman Meltzer suggests that there is a unique law regarding sanctified birds, so that the owner retains some level of ownership of the bird even after committing it as a sacrifice. If this is true, the Rambam’s position is easier to understand.