הלכה על במדבר 35:12

To not kill someone liable before he is brought to justice: That we were prevented not to kill the sinner when we see him doing a sinful act for which he is liable the death penalty, before we bring him to court. Rather, we are obligated to bring him before the court and we bring witnesses in front of [the judges] and they sentence him to what he is liable, as it is stated (Numbers 35:12), "and the killer shall not die before his standing, etc." And the language of the Mekhilta (Sifrei Zuta on Numbers 35:12) is \'Perhaps they should kill him from when he killed or was adulterous? [Hence] we learn to say, 'and the killer shall not die before his standing, etc.'" And even if the Great Court saw him kill, they would all be witnesses and take their testimony to another court to judge him. And they also said in Mekhilta (Sifrei Zuta on Numbers 35:12), "Behold, a community that saw one kill a soul, perhaps they should kill him before he stands in court? [Hence] we learn to say, 'and the killer shall not die before his standing.'"