In the Law, Yahweh was saying to Israel, Blood must be shed before sinful man can have a relationship with My holiness. Don't you understand? The only blood sufficient for this is My own!
So God Himself came to earth, Love itself in the form of the God/Man Jesus of Nazareth. To live, to teach, to suffer, and to die. He came to spill His own blood upon the sacrificial altar: the Lamb of God who takes away the sin of the world...