Deuteronomy 21:9

9 And thou shalt be free from the innocent’s blood, that was shed, when thou shalt have done what the Lord hath commanded thee.

Deuteronomy 21:9 Meaning and Commentary

Deuteronomy 21:9

So shalt thou put away the guilt of innocent blood from among
you
Which otherwise, the person not being found out, and brought to just punishment for it, would devolve upon the whole. Aben Ezra interprets it the punishment of innocent blood, which, by the above method being taken, would not be inflicted on them:

when thou shalt do that which is right in the sight of the Lord;
as it was to observe this law concerning the beheading of the heifer, with all the rites and ceremonies belonging to it here enjoined; as well as every other command, statute, and ordinance of the Lord, which are all right to be done, ( Psalms 19:8 ) .

Deuteronomy 21:9 In-Context

7 And shall say: Our hands did not shed this blood, nor did our eyes see it.

8 Be merciful to thy people Israel, whom thou hast redeemed, O Lord, and lay not innocent blood to their charge, in the midst of thy people Israel. And the guilt of blood shall be taken from them:

9 And thou shalt be free from the innocent’s blood, that was shed, when thou shalt have done what the Lord hath commanded thee.

10 If thou go out to fight against thy enemies, and the Lord thy God deliver them into thy hand, and thou lead them away captives,

11 And seest in the number of the captives a beautiful woman, and lovest her, and wilt have her to wife,