Halakhah sur Les Nombres 35:31

He prohibited the taking of ransom from an intentional murderer. Rather he must be killed under any circumstances. And that is His saying, "And you shall not take ransom for the soul of a murderer who is liable for death" (Numbers 35:31). And the regulations of this commandment have already been explained in Makkot. (See Parashat Masei; Mishneh Torah, Murderer and the Preservation of Life 5.)

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."