廣弘明集 13.106

13.106

外論曰。老君初誕之日既不同凡。晦迹之時故當殊世。所以西之流沙途經函谷。青牛出境紫氣浮天。不測始終莫知方域。釋迦抱危疾於舍衛。告殞命於雙林。燒柩焚屍還同胡法。氣盡神謝曾不異凡。此去世之異七也。

The external treatise says: Since the day of Lord Lao’s birth was already unlike that of ordinary men, the time of his concealing his traces was naturally distinct from the world. Thus, heading west to the shifting sands, his journey passed through Hangu Pass; the green ox crossed the border, and purple vapor floated in the sky. None could fathom his beginning or end; none knew his whereabouts. Śākyamuni caught a grave illness in Śrāvastī and announced his demise in the Twin Groves; burning the coffin and incinerating the corpse followed the customs of the barbarians. His breath finished and spirit departed, in no way different from ordinary men. This is the seventh distinction in departing the world.