The process of a metzora’s purification, as the Torah outlines in Parashat Metzora (14:1-32), includes the offering of three sacrifices – an asham (guilt-offering), a chatat (sin-offering), and an ola (burnt-offering). An ordinary metzora, the Torah instructs, brings three sheep – two male, for the asham and ola, and a female for the chatat. If, however, the metzora is poor, and cannot afford three sheep, then he offers one sheep as an asham and two birds (which are less expensive than sheep) for the chatat and ola.
The Mishna in Masekhet Negaim (14:12) establishes that if a poor metzora, who is permitted to bring the less expensive sacrifice, nevertheless chooses to bring the standard sacrifice, then he fulfills his obligation. The Rash Mi-Shantz, in his commentary to the Mishna, adds that this halakha applies not only be-di’avad – after the fact, if a mistake was made – but even le-khatechila (from the outset). Meaning, a poor metzora is fully entitled to choose to offer the more expensive sacrifice. In fact, the Rash Mi-Shantz adds, this would be a praiseworthy measure (“tavo alav berakha”).
The Mishneh Le-melekh (Hilkhot Shegagot 10:13) observes that the Mishna’s ruling would seem to disprove the controversial position taken by the Sefer Ha-chinukh (123) regarding the similar case of a korban oleh ve-yoreid. Earlier in Sefer Vayikra (5:1-13), the Torah requires the violator of certain transgression to offer a sheep as a chatat, but if the individual cannot afford a sheep, he may bring instead two birds – one as a chatat, and the other as an ola. In that case, the Chinukh maintains, a poor man does not fulfill his obligation if he decides to offer the more expensive sacrifice despite his difficult financial condition. The Mishneh Le-melekh raises the question of why the Chinukh disqualifies a standard korban oleh ve-yoreid offered by a poor person, in light of the fact that the Mishna explicitly allows – and perhaps even encourages – a poor metzora to offer a standard sacrifice.
A number of writers (Sefat Emet, Yoma 41b; Rav Yerucham Perlow, in his commentary to Rav Saadia Gaon’s listing of the mitzvot, asei 144) suggested a fairly simple reason to distinguish between the two cases. In the case of a metzora, he brings the same three kinds of sacrifices – a chatat, ola and asham – regardless of his financial status. The only difference between a regular metzora and an impoverished metzora is that the latter brings birds instead of sheep for the chatat and ola. In the case of a korban oleh ve-yored, by contrast, the standard offering consists of just a chatat, whereas the poor person’s sacrifice includes both a chatat and ola. The impoverished individual’s sacrifice is less expensive – consisting of two small birds, the combined cost of which is less than that of one sheep – but it includes two sacrifices, and not just one. Hence, since the Torah requires him to offer both a chatat and an ola, he cannot offer the more expensive sacrifice, which consists of only a chatat.
A different answer is offered by Rav Yaakov Ettlinger, in his Arukh La-ner commentary to Masekhet Keritut (28a). The Gemara there cites a textual source for the halakha permitting an impoverished metzora to bring a standard sacrifice, clearly implying that intuitively, we would have assumed that he fulfills his obligation only with the sacrifice assigned by the Torah for the poor. It is only because of a nuance in the text that Chazal concluded that a poor metzora is given the right to offer the more expensive sacrifice. Naturally, then, in the case of a korban oleh ve-yored, where no such textual inference is made, a poor man cannot fulfill his obligation with a wealthy man’s sacrifice.
(See Rav Yechiel Tzik’s Yekara De-orayta, Parashat Metzora)