Halakhah zu Bamidbar 28:31

The commandment of the sacrifice being unblemished: That every sacrifice that we sacrifice be perfect from blemishes that come in Scripture and from those that the tradition comes about that they are blemishes for its specie. And that is [the understanding of] what is stated about this (Leviticus 22:21), "unblemished shall it be acceptable." And they said in Sifra, Emor, Section 7:9, "'Unblemished shall it be' - is a positive commandment." And they brought a proof (Menachot 87a) that the libations and flours and oils [also] be completely perfect from degeneration from that which is written (Numbers 28:31), "they shall be unblemished, and their libations."