Parashas Metzora · Passuk 14:21
Chabad.org — English translation + Rashi
Torah Temima points to Arachin 17a (verified on the daf).
E-Daf.com — Tsurras Hadaf (size=3)
HebrewBooks / Shas PDF of the daf
English: “And if he is poor” — if someone said “the offering of this metzora is upon me,” and the metzora was poor but the one who vowed is rich, he brings the rich man’s offering. Why? The Torah said “and if he is poor,” but this one is not poor.
Status of the one who vows
Chazal teach that when a third party undertakes the metzora’s offering, the financial status of the one who vows determines which offering is brought.