首楞嚴義疏注經 2.120

2.120

指喻能詮言教，月喻所詮真理。若欲見月，須亡指以觀之。若欲見性，須亡言而體之。不能亡言，豈能見性？不能遺指，豈識月輪？《圓覺》云「修多羅教如標月指，若復見月，了知所標畢竟非月，一切如來種種言說開示菩薩亦復如是。」指月俱迷，詮旨兩失，在文可見。

The finger is an analogy for the verbal teaching that expresses (vācaka); the moon is an analogy for the true principle that is expressed (vācya). If one wishes to see the moon, one must forget the finger in order to view it. If one wishes to see the nature, one must forget words in order to embody it. If one cannot forget words, how can one see the nature? If one cannot leave behind the finger, how can one recognize the moon's disc? The Sūtra of Perfect Enlightenment says: 'The sūtra teachings are like a finger pointing at the moon; if one sees the moon, one completely knows that what points is ultimately not the moon. All the various spoken teachings of the Tathāgatas to instruct the bodhisattvas are also like this.' Being deluded regarding both finger and moon, and losing both the expression and the intent, is clearly visible in the text.