首楞嚴義疏注經 2.137

2.137

緣心若是真性，應如其主，何得隨聲來去？以離聲時無分別故。豈同真心周遍法界，湛然常住。隨聲之心既然，隨色之心亦爾，故云豈唯等。

If the conditioned mind were the true nature, it ought to be like the host; how could it come and go with sound? Because when apart from sound, it lacks discrimination. How could it be identical to the true mind, which pervades the dharmadhātu and is clear and permanently abiding? Since the mind that follows sound is like this, the mind that follows form is also like this; hence [the text] says 'how could this apply only', etc.