84 Shekalim 2/2-5

(2) One who gives his shekel to his fellow to donate on his behalf, and [his fellow] donates it for himself: if the terumah was set aside, he [has committed the sin of] misappropriation. One who donates his shekel from hekdesh [consecrated funds]: if the terumah was set aside, and an animal [bought from the funds] was already sacrificed, he [has committed the sin of] misappropriation. If [he drew his shekel donation] from ma'aser sheni [second-tithe] funds or shevi'it [seventh-year] funds, he must [redeem that money] and eat that amount.

(3) One who is accumulating coins and says, these are for my shekel, Beit Shammai says, the extra must be used as a free-will offering. Beit Hillel says that the extra is not consecrated [as a free-will offering]. [If one were to say that] I will bring from these for my shekel, they both agree that the extra is chullin [not consecrated]. [If one were to say that] these are for a chattat [sin-offering], they both agree that the extra must be used as a free-will offering. [If one were to say that] I will bring from these for a chattat, they both agree that the extra is chullin.

(4) Rabbi Shimon said, what is the difference between shekalim and the chattat offering? Shekalim have a fixed amount, while a chattat does not have a fixed amount. Rabbi Yehuda said, even shekalim don't have a fixed amount because when the Jews ascended [to Israel] from the [Babylonian] exile they would pay the shekel in darkonot [equivalent to 4 shekels]; then they paid in selaim [equivalent to 2 shekels]; then they paid in selaim [equivlant to 1 Mishnaic shekel or half a Toraitic shekel] and they sought to pay in dinarim [equivelant to 1/2 of a Mishnaic shekel]. Said Rabbi Shimon, even so, everyone would give an equal amount [at any given time period]. But [for a] chattat, this one brings [an offering worth] a sela, this one brings [an offering worth] two, and this one brings [an offering worth] three.

(5) The excess funds of [money set aside for] the shekalim is not sanctified. The excess funds [of money set aside for] the tenth of an eifah [of flour brought with a chattat offering], the excess funds of the offerings of zavim [males with abnormal genital discharge], the offerings of zavot [females with abnormal genital discharge], the offerings of women who gave birth, chattat offerings and asham [guilt] offerings, their excess funds must be given as a free-will offering. This is the general rule, everything that comes for the sake of a chattat or asham offering, their excess funds must be given as a free-will offering. The excess funds of an olah [burnt offering] is for an olah. The excess funds of a minchah [meal offering] is for a minchah. The excess funds of a shelamim [peace offering] is for a shelamim. The excess funds of the pesach offering is for a pesach offering. The excess funds for a nazirite's offering is for a nazirite's offering. The remainder for an individual nazirite must be given as a free-will offering. The excess funds [given] for the poor is for the poor. The excess funds [given] for an individual poor person is for that poor person. The excess funds [given] for captives is for captives. The excess funds [given] for a specific captive is for that specific captive. The excess funds [given] for the dead is for the dead. The excess funds for a specific dead person is for his inheritors. Rabbi Meir said, the excess funds for a specific dead person is set aside until Eliyahu comes. Rabbi Natan said, the excess funds for a specific dead person is used to build a gravestone on his grave.