瑜伽論記 6.377

6.377

九、本生者，此說世尊因地從初發心起行已來所經死生行難行等，名本生。

Ninth, 'birth stories' (jātaka): this speaks of the deaths and rebirths undergone by the World-Honoured One on the causal ground from his initial aspiration and undertaking of practice onward, practicing what is difficult to practice, and so forth; these are called birth stories.