This is metaphorical language. Death is to silence someone for good. God hears the blood screaming. A blatant injustice has been committed and God will not let it go unpunished. God stands up for the oppressed and disenfranchised. Christ points to the endless flow of blood that began with Abel and continued into his days (Matthew 23:35). Christ indicates that it is imputed to you if you do not follow him. The killing continues to this day. Not a drop of that innocent blood remains unavenged. There will be a final judgment (Revelation 20:1–15). That injustice does not just remain in the picture with God. It rings in his ear, his heart, he calls it a cry. Human blood is precious, especially that of his children (Psalm 116:15). God is going to respond. Those who do not seek salvation in the more powerful blood (Hebrews 11:24) of Christ will have to bear their own punishment (Luke 11:51). Abel’s blood only cries out for vengeance. Christ’s blood makes atonement. That is its power, infinitely greater than the cry for revenge.
10 And the LORD said, “What have you done? The voice of your brother’s blood is crying to me from the ground.