Midrasch zu Wajikra 27:11

1) (Vayikra 27:11) ("And if any unclean beast, which may not be presented of it as an offering to the L–rd, then the beast shall be stood before the Cohein.") I might think that Scripture is speaking of a beast which is (ritually) unclean. But (Vayikra 27:27) "And if among the unclean beasts, then he shall redeem it with your valuation" already speaks of a (ritually) unclean beast. Our verse, then, must be referring to the redemption of consecrated animals which became blemished. I might think that it must be redeemed even if it contracted a passing blemish; it is, therefore, written "which may not be presented of it as an offering to the L–rd" — to exclude a (beast with a) passing blemish, which is kasher (for sacrifice) when the blemish passes.

2) "unclean": to include (in redemption) a dead (literally unclean) beast which he consecrated (for its money value). I might think that (it is redeemed) even if he said "This beast is consecrated" and (then) it died; it is, therefore, written "then the beast shall be stood … (Vayikra 27:12) and the Cohein shall valuate it." Where there is "standing," there is valuation; where there is no standing, there is no valuation.

3) Why do you see fit to include (his consecrating) a dead beast, and exclude his saying "This beast is consecrated" and its dying (thereafter)? — After Scripture includes, it excludes. We derive it from an unclean (i.e., blemished) beast. Just as with an unclean beast, the time of its redemption is equivalent to the time of consecration (i.e., at both times the beast is not fit for sacrifice), so, I include (his consecrating) a dead beast, whose time of redemption is equivalent to its time of consecration, and I exclude his saying "This beast is consecrated" and its dying (thereafter), where the time of its redemption is not equivalent to its time of consecration.