弘明集 6.15

6.15

論稱。佛經云。釋迦成佛已有塵劫之數。或為儒林之宗國師道士（此皆成實正經非方便之說也）。

The treatise cites: 'A Buddhist scripture says: "Since Śākyamuni attained Buddhahood, dust-particle kalpas have already passed. At times he manifested as the master of the Confucian scholars, the state preceptor, or a Daoist master."' (These are all authentic, established scriptures, not expedient explanations.)