Man's life is in the blood. Life for life =blood for blood, Oxygen is carried to our bodies by the blood
Gen 9:4 But flesh with
the life thereof, which is the blood thereof, shall ye not eat.
5 And surely
your blood of your lives will I require; at the hand of every beast will I require it, and at the hand of man; at the hand of every man’s brother will I require
the life of man.
6 Whoso sheddeth man’s blood, by man shall his blood be shed: for in the image of God made he man.
Able's blood cried to God
Ge 4:10 And he said, What hast thou done?
the voice of thy brother’s blood crieth unto me from the ground. {blood: Heb. bloods }
Ge 4:11 And now art thou cursed from the earth, which hath opened her mouth to receive thy brother’s blood from thy hand;
Christ's blood, better
Heb 12:24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.