Sefer HaChinuch ספר החינוך

To not kill the innocent: To not kill a soul, as it is stated (Exodus 20:13), “You shall not kill.”

The root of this commandment is well-known and revealed to all that see the sun. As God, may He be blessed, created the world and commanded us be fruitful and multiply, in order to settle it in front of Him. And [so] He prevented us, that we not destroy it with our hands, to kill and destroy the creatures which are the settlers of the world. However, the total evildoers — for example, the heretics and the talebearers — are not from the settlers of the world. And about them, the verse states (Proverbs 11:10), “with the destruction of the evildoers is there glee” — because they do not settle (civilize) the world, but rather destroy it with all their might. And this is what one sage from our Sages, may their memory be blessed, said about the destruction of the evildoers (Bava Metzia 83b), “I am ridding the thorns from the vineyard” — meaning to say that with the destruction of these, the world will be more settled, [just] like with the removal of thorns (weeds), the fruits of the vineyard multiply and are better.

From the laws of this commandment — that which they, may their memory be blessed, said (Sanhedrin 88a) [that] it is the same whether one kills a healthy person or a sick person close to death, and even if he is dying from a sickness by the hand of the Heavens, he is [still] killed for it; the law of the trial of a murderer; and the rest of its details — are elucidated in the ninth chapter of Sanhedrin and the second chapter of Makkot. (See Tur, Choshen Mishpat 425.)

And [it] is practiced in every place and at all times by males and females. And we kill with the sword one who transgresses it and kills volitionally, [if] there are witnesses who warned him (Sanhedrin 71b). About inadvertence, we will write its law below, with God’s help, in the Order of Eleh Masei (Sefer HaChinukh 409).