Midrash sobre Exodo 29:2

"soleth" (fine flour): Just as soleth elsewhere (Shemoth 29:2) is of wheat, so, here.

5) "a tenth of an ephah": one-tenth of three sa'in, which is seven revi'in and an addition. "soleth": Just as soleth stated there (Exodus 29:2) is of wheat, so soleth stated here is of wheat. "for a sin-offering": Its monies must be designated as being for a sin-offering. "he may not place oil upon it": But he may place (oil) upon what remains (of the minchah offering). "he shall not put frankincense upon it": I might think that if he did place frankincense upon it, it becomes unfit; it is, therefore, written: "for it is a sin-offering" (and just as a beast sin-offering is not invalidated by frankincense, this bird sin-offering is, likewise, not invalidated by frankincense. Or, (I might think): "it is a sin-offering" — Even if he placed oil upon it, it is kasher; it is, therefore, (to negate this) written: "it" (with frankincense, is a sin-offering — but not with oil). And why do you see fit to permit it with frankincense and to invalidate it with oil? After Scripture includes, it excludes. Why do I permit it with frankincense? Because it can be picked off — and I invalidate it with oil, because it cannot be picked off.

5) "meal" (soleth): Just as the soleth mentioned elsewhere (Shemoth 29:2) is wheat, so the soleth mentioned here is wheat. "a meal-offering": like all meal-offerings, requiring a fistful. "perpetual": even in a state of tumah, even on the Sabbath.