Midrash su Levitico 27:27

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.

1) (Vayikra 27:27) ("And if [he wishes to redeem] an unclean beast [that he dedicated to Temple maintenance], then he shall redeem it according to your valuation, and he shall add its fifth upon it. And if it is not redeemed, then it shall be sold by your valuation.") "And if an unclean beast, then he shall redeem it according to your valuation." What is the intent of this? Because it is written (Vayikra 27:25) "according to the shekel of the sanctuary," I might think (that he can redeem) only with that. Whence do I derive for inclusion any movable object? From "then he shall redeem"; but on condition that he assesses (the object) monetarily (to coincide with the worth of the animal), e.g., if he said: "This garment for this ass," the latter becomes chullin (non-consecrated) and he must cover any arrears (between the worth of the animal and the worth of the garment).

2) "and he shall add its fifth upon it": So that it and the fifth make five (equal parts [as opposed to a fifth of the principal], i.e., he divides the principal by four and adds a fifth part [e.g., if the principal were twenty, he pays twenty-five]).