'Innocent Blood' in the Bible

Now you also know what Joab the son of Zeruiah [my sister] did to me, and what he did to the two commanders of the armies of Israel, to Abner the son of Ner and to Amasa the son of Jether, [both of] whom he murdered; avenging the blood of war in [a time of] peace. And he put the [innocent] blood of war [of Abner and Amasa] on his belt that was around his waist, and on his sandals on his feet.

And the king said unto him, Do as he hath said, and fall upon him, and bury him; that thou mayest take away the innocent blood, which Joab shed, from me, and from the house of my father.