《礼记·郊特牲》
至于以肺、肝、心作为供品祭神，是看重它们是滋生生气的器官。
告幽全之物者，贵纯之道也。血祭，盛气也。祭肺肝心，贵气主也。
As for using lungs, liver, and heart as offerings to sacrifice to the gods, this is because they are the organs that support the vitality.