佛說觀佛三昧海經 2.39

2.39

佛告父王：「如來白毛，自從初生乃至成佛，於其中間微細小事可得觀見。既成佛已，白毫光明眾相具足，諸修多羅中佛已廣說，白毫相光究竟之處，十地菩薩爾乃得見，先說小者，應諸世間此事易見。」

The Buddha told his father the king: “Regarding the Tathāgata’s white hair, from its first arising up to his attainment of buddhahood, the subtle and minor matters between them may be observed and contemplated. Once he had attained buddhahood, the light of the white ūrṇā was complete with all marks, as the Buddha has already explained extensively in the sūtras. The ultimate reach of the light of the white ūrṇā mark can only then be seen by bodhisattvas of the tenth ground; the minor aspects were spoken first, as these are easy for the world to see.”