首楞嚴義疏注經 2.114

2.114

佛以言音詮此真性，今我領解復是緣心。所悟真性、能悟緣心，還同如來前所責言：「如汝今者承聽我法，此則因聲而有分別。有何別耶？」由是未敢認為心地。心有能生可依止義，喻之地也。言圓音者，以佛一一語言遍窮生界，而其音韻常不雜亂，如《起信疏》解。

The Buddha expresses this true nature through the sounds of words, and now my comprehension is again the conditioning mind. What is the difference between the true nature that is awakened to and the conditioning mind that awakens, and the Tathāgata's earlier reproach: 'Just as you now listen to my Dharma, this is having discrimination because of sound'? Therefore, he does not dare recognize it as the ground of mind. The mind has the capacity to produce and can be relied upon, which is compared to the ground. "Complete sound" refers to how every word of the Buddha completely reaches all realms of sentient beings, while its sounds and tones are never confused, as explained in the Commentary on the Awakening of Faith.