金剛般若波羅蜜經註解 1.228

1.228

既云如來色身相好，不可得見，如何為人演說法耶？然如來悲願深重，隨感而應，無說而說、說即無說，不達此意是為謗佛。

Since it was said that the Tathāgata's physical body, marks, and characteristics cannot be seen, how does he expound the Dharma for people? Yet the Tathāgata's compassionate vows are profound and weighty: responding in accord with what is sensed, he preaches without preaching, and his preaching is itself no-preaching. Not understanding this meaning constitutes slandering the Buddha.