Q:

Why "אֲשֶׁר תַּשִּׂיג יָדוֹ" in Lev. 14:22?

M'tzora 14:21–22 discusses the korbanos (sacrifical offerings) brought by someone after he's done being a m'tzora:

וְאִם דַּל הוּא וְאֵין יָדוֹ מַשֶּׂגֶת וְלָקַח כֶּבֶשׂ אֶחָד אָשָׁם לִתְנוּפָה לְכַפֵּר עָלָיו וְעִשָּׂרוֹן סֹלֶת אֶחָד בָּלוּל בַּשֶּׁמֶן לְמִנְחָה וְלֹג שָׁמֶן. וּשְׁתֵּי תֹרִים אוֹ שְׁנֵי בְּנֵי יוֹנָה אֲשֶׁר תַּשִּׂיג יָדוֹ וְהָיָה אֶחָד חַטָּאת וְהָאֶחָד עֹלָה.‏
If he is poor, and his [spending] power does not reach [the korbanos a more wealthy person can bring], then he takes… and two turtledoves or two young doves, which [or: whichever] his [spending] power can reach. One shall be a chatas-offering; the one, an ola-offering.

The words "אֲשֶׁר תַּשִּׂיג יָדוֹ / which [or: whichever] his [spending] power can reach" seem superfluous. Why are they there?
(And if your answer seems like it should apply not only to m'tzora but to any instance of a poor man's korban, then it should explain why these words are here only and not in 5:7 or 12:8.)

A:

The Sifra there (12) explains that this is coming to include even a case where he was rich at the time he was healed from the Tzora'as, and only later became poor - he would still bring a poor man's sacrifice, and we don't say that he has to bring according to what he could afford when he became obligated. See Malbim there for further explanation.

