金剛經纂要刊定記 5.299

5.299

是名下。以彼色等雖非質閡之一切，乃是即性之一切，今約此義故曰真如。揀異色等無性，故云自性也。

"Are called..." and so forth: although those forms and so forth are not all things in the sense of physical obstruction, they are all things in the sense of being identical to the nature. Now, taking this meaning, it is therefore called tathatā. To distinguish it from form and the rest lacking self-nature, it is therefore called "own-nature."