Mitzvah 285-286) That we should not sanctify blemished animals, and that the offering should be perfect
“Anything which has a blemish you shall not offer… it shall be perfect to be accepted!” (Vayikra 22:20-21)
It is a negative commandment that we should not sanctify blemished animals to offer them on the altar. This applies even if he has not offered them, as with the act of consecrating them for an offering one has already transgressed a negative commandment, and about the sanctification itself it says “Anything which has a blemish you shall not offer!”.
Amongst the roots of the commandment are that which has already been explained when discussing a blemished person entering the temple, as because of the preciousness of the temple and its glory it is fitting that there should be no blemishes at all.
This commandment applies in all places and at all times, both to men and women. Anyone who transgresses this and consecrates a blemished animal, even nowadays, has transgressed this sin.
It is a positive commandment that every offering that we offer should be perfect without a blemish. This includes both the blemishes which the Torah enumerates explicitly and those which were transmitted to Chazal, as it says “It shall be perfect to be accepted!”.
The root of this commandment is obvious, as we have already explained that the point of offering animals to Hashem is to awaken and concentrate the tjhoughts of a person to Hashem, for a person is effected by the power of his actions. It is therefore correct that the offering should be unblemished, for a person will be more affected by an important perfect offering. The above is obvious to any thinking person.
This commandment applies when the temple was standing. If one takes a blemished animal and slaughters it, sprinkles its blood on the altar or offers up its fats etc., he has violated this commandment, besides for having transgressed a negative commandment as has already been discussed.