首楞嚴義疏注經 5.439

5.439

專憶如佛，專忘謂不念者。如是眾生見佛不定，故云若逢不逢等。

The one who exclusively remembers is like the Buddha; the one who exclusively forgets refers to the one who is not mindful. Such sentient beings seeing the Buddha is indeterminate; therefore it says 'if they meet, it is as if they had not met,' and so forth.