金剛經纂要刊定記 2.110

2.110

Because it possesses superior capacity, it is said to be 'utterly hard and utterly sharp', which serves as a metaphor for prajñā. From 'No object...' downward explains the characteristics of being utterly hard, and so on. One then knows that if there were a single object that could destroy it, it would not be utterly hard; and if there were a single object it could not shatter, it would not be utterly sharp. Just as silver and iron, though hard, melt when encountering fire, and knives and swords, though sharp, chip when striking stone, they are not utterly hard or sharp. To distinguish it from other hard and sharp things, the word 'utterly' is added.