金剛經纂要刊定記 5.298

5.298

由色等者。謂色等即空，故非色等，如像即鏡故非像等。斯約諸法即真，顯非法真如等者，謂空中必無色也。以彌滿清淨中不容他故，此約真中無法解非法也。備斯二義，故曰即非。

"Due to form and the rest": this means that form and the rest are identical to emptiness and therefore are not form and the rest, just as a reflection is identical to the mirror and therefore not a reflection and so forth. This explains "not dharmas" from the standpoint of all dharmas being identical to the real. "Tathatā..." and so forth means that within emptiness there is definitely no form, because within pervasive purity nothing else is admitted; this explains "not dharmas" from the standpoint that within the real there are no dharmas. Endowed with these two meanings, it is therefore called "are not."