金剛經纂要刊定記 3.45

3.45

"Manifested traces" refers to the manifested traces of transformation. "What is expressed": whatever the buddhas do is never haphazard, but always uses external phenomena to express the internal body and mind. For instance, when expounding the Tathāgatagarbha Sūtra, his entire body emitted light, within the light flowers appeared, and when the flowers withered, buddhas were seen. Thereupon Ānanda questioned the Buddha, and the Buddha expounded it for him. Just as in the Avataṃsaka Sūtra, which speaks of "buddhas and bodhisattvas speaking of the heavens, clouds, Mount Sumeru, the great ocean, and so forth," all have something expressed. In all these cases, external phenomena serve as what can express, and the Dharma serves as what is expressed; since it is not in vain, it is said to be "must."