Midrasch zu Wajikra 14:21

1) (Another proof for the above") R. Yehudah b. Betheirah says: It is written (Vayikra 14:21): "And if he is poor … (then he brings) a tenth-part of fine flour." Just as we find that a poor man brings one beast and one tenth-part, so a rich man, who brings three beasts, brings three tenth-parts. How, then, am I to satisfy "and three tenth parts of (an ephah of) fine flour for a meal-offering mixed with oil"? (That it is to be understood as) for the beasts.

1) (Vayikra 14:21) ("And if he is poor, and his hand cannot attain, then he shall take one he-lamb as a guilt-offering to be waved to make atonement for him, and one tenth part of fine flour mixed with oil as a meal-offering, and a log of oil.") "And if he is poor": By this I might think that if he became poorer than he was (when he incurred responsibility for the offering), such as one who possessed one hundred manah who was reduced to fifty manah (— I might think that such a one could be called "poor" and not liable for a rich man's offering). It is, therefore, written "and his hand cannot attain." If "and his hand cannot attain," (I might think that) if he had the means but could not readily find (the needed sheep — I might think that such a one could bring a poor man's offering). It is, therefore, written "and he is poor" — so that both verses are necessary, lacking which we would not know (the halachah).

2) "and if he is poor": he and not its vowers. Because since in valuations, a poor man who takes upon himself a rich man's valuation, gives a poor man's valuation, I might think that even a poor man who said: "The offering of this leper is upon me (to give"), if the leper were rich, (I might think) he brings a poor man's offering; it is, therefore, written "he", and not its vowers.