IN THE PARSHAH:
After a מְצוֹרָע becomes טָהוֹר, he must bring certain קָרְבָּנוֹת, depending on what he could afford.
The more expensive קרבנות are called קָרְבַּן עָשִׁיר, the less expensive קרבנות are called קָרְבַּן עָנִי.
Interestingly, another Yid may volunteer to bring these קרבנות on behalf of the מצורע, instead of the מצורע himself.
The רמב"ם writes that an עשיר (a “wealthy” person) who pledges to bring the קרבן of a מצורע who is an עני (a “poor” person) must actually bring a קרבןָ עשיר, the more expensive קרבנות.
QUESTION:
Since he pledged to bring the קרבן of a poor מצורע, why must he bring the קרבן of an עשיר?
ANSWER:
If all he had to do was fulfill his נֶדֶר, it would indeed be enough for him to bring a קרבןָ עני, which is the amount that he pledged.
However, these קרבנות are also meant to bring about a כַּפָּרָה, atonement, for the מצורע.
Although he himself did nothing wrong, he is able to bring about atonement for the מצורע because all Yidden are responsible for one another (כָּל יִשְׂרָאֵל עֲרֵבִים זֶה בָּזֶה).
When he pledged to bring the קרבנות for the מצורע, he put himself in the place of the מצורע, as if he himself was the מצורע and needs to bring about כפרה for himself.
So since he is an עשיר, he must bring a קרבןָ עשיר, which is what he could afford.
Further discussion:
Since it becomes his own obligation, why does an עני who pledges to bring the קרבן of a מצורע עשיר have to bring a קרבןָ עשיר? (See אות ה in the שיחה)
