古代帝王赐给功臣享有世袭爵位和免罪等特权的证件时，宰白马歃其血，以示坚守誓约，后人称为“丹书白马” Emperors of the hereditary title of nobility given to meritorious and impunity enjoyed special privileges such documents, the slaughter horse drink his blood, to show stick to their vows, later known as the "Dan White Horse Book"