Numbers 35:33 'So you shall not pollute the land in which you are; for blood pollutes the land and no expiation can be made for the land for the blood that is shed on it, except by the blood of him who shed it.

Deuteronomy 21:1 "If a slain person is found lying in the open country in the land which the LORD your God gives you to possess, and it is not known who has struck him,

Hebrews 12:24 and to Jesus, the mediator of a new covenant, and to the sprinkled blood, which speaks better than the blood of Abel.

Revelation 6:9 When the Lamb broke the fifth seal, I saw underneath the altar the souls of those who had been slain because of the word of God, and because of the testimony which they had maintained;

Revelation 6:10 and they cried out with a loud voice, saying, "How long, O Lord, holy and true, will You refrain from judging and avenging our blood on those who dwell on the earth?" (NASB ©1995)