佛祖統紀 35.145

35.145

○左慈見漢祚將終。乃入天柱山。學道得金液九丹經於石室。能變化萬端。曹操聞而召之欲從學。慈曰。學道當清淨。非尊貴穢淫所宜也。操欲殺之。人見慈斷其頭以獻。及視之乃一束茅耳。後與弟子葛仙翁別入霍山。合丹仙去。

Zuo Ci, seeing that the Han dynasty's mandate was about to end, entered Mount Tianzhu, studied the Dao, and obtained the Scripture of the Nine Elixirs of Gold Fluid in a stone chamber. He was able to transform in myriad ways. Cao Cao heard of him and summoned him, wishing to study under him. Zuo Ci said: 'Studying the Dao requires purity; it is not suitable for the exalted, defiled, and licentious.' Cao Cao wished to kill him. Someone saw Zuo Ci, cut off his head, and presented it; upon looking at it, it was merely a bundle of cogongrass. Later, Zuo Ci parted with his disciple Immortal Ge and went to Mount Huo, where he compounded the elixir and ascended as an immortal.