The blood is the life-current in a person, the red stream carrying the spirit's charge through every vessel, and it is this inner life that cleanses, not an outside sacrifice. The Christ is the awakened higher self, faithful because it watches without wavering, and first-begotten of the dead because it is the first thing in a person to rise out of the sleeping flesh into full awareness. To be washed in its own blood is for the animal nature to be flooded and purified by that same rising life already in the veins.
The kings of the earth are the strong bodily drives this higher center governs from within. When the awakened self rules them, the old stains of appetite dissolve in the very life that gave them.
Blood: the life-current in the veins, the spirit's charge that cleanses and renews the whole body
Kings of the earth: the strong bodily drives and powers that the higher self rules from within