首楞嚴義疏注經 5.316

5.316

非今一佛所說法門，河沙佛所聞祕密法，我皆為眾宣說無畏。言微妙者，巧以言辭、譬喻方便隨順機感也。

It was not just the Dharma gates spoken by this one Buddha; the secret Dharma heard at the dwellings of Buddhas as numerous as the sands of the Ganges, I have expounded without fear for all assemblies. Calling it 'subtle' means skillfully using words, similes, and expedients to accord with capacities and receptivity.