Sefer HaChinuch ספר החינוך

Not to take ransom to save the murderer from the death penalty: Not to take ransom, meaning to say, redemption [money] — and even all the money in the world — to save the soul of a murderer, such as not to kill him, as it is stated (Numbers 35:31), “You shall not take ransom for the soul of a murderer who is guilty for death.”

And the root of this commandment is well-known — as if the rulers of the land allowed to take ransom from the hand of the murderer, it would come out that anyone greater and wealthier than his fellow would kill him if he got angry at him and give his ransom. And it would come out that the sword of a man would be upon his brother and civilization would be [destroyed].

From the laws of the commandment is that which they, may their memory be blessed, said (Ketuvot 37b) that even if the blood redeemer wants to exempt him [from the death penalty] and says to the judge that he forgives his blood and that they will take ransom from him — [even] if they want, they are not allowed to take ransom and to exempt him for all of the money in the world; but rather he is killed, like the command of God upon us. And the rest of its details are in Tractate Makkot. (See Mishneh Torah, Laws of Murderer and the Preservation of Life 1.)

And [it] is practiced at the time of the [Temple] by males and females, as at this time we have no involvement with capital punishments. And they say about [this] that this prohibition is also practiced by females, even though they do not judge. And the matter is that if maybe at the time of [now] [the Temple] (in the Vilna edition, that time) because of some reason, it will come to the hand of a woman that they will ask from her to save the soul of a murderer on account of money, that she is warned not to take the money and to save him, due to this negative commandment. And one who transgresses this — whether a man or whether a woman — and takes money to save the murderer violates this negative commandment; and his punishment is very great, as it is a cause for the loss of many souls of Israel.