金剛經纂要刊定記 7.171

7.171

三法不定者。有三釋：一則苦樂捨三受不定也。二則受想因於三法而不定，三法即違順等三境也。三則受想觸為三，三皆不定也，以一不定餘皆不定故。然此雖說想觸，意明於受，如風水相投即有泡起，觸想和合則有受生，是故以泡喻於受也。故大雲云：「水上之泡出沒不定，心中之受苦樂不常。」

"Three dharmas are indeterminate": there are three explanations: 1. The three sensations of suffering, pleasure, and equanimity are indeterminate. 2. Sensation and perception are indeterminate due to three dharmas, the three dharmas being the three realms of discordant, concordant, etc. 3. Sensation, perception, and contact form the three, and all three are indeterminate, because when one is indeterminate the others are all indeterminate. However, although this mentions perception and contact, the intention is to clarify sensation: just as when wind and water meet, bubbles arise, when contact and perception combine, sensation arises; therefore bubbles symbolize sensation. Thus Dayun says: "Bubbles on water appear and disappear indeterminately; sensations in the mind—suffering and pleasure—are inconstant."