折疑論 5.52

5.52

聽之不能聞（經云。聽之不聞。名曰希。希者無聲之謂。其道故無聲可聞）。

Listening to it, it cannot be heard. (The sūtra says: "Listening to it, it is not heard; it is called the soundless (xi)." Xi refers to being without sound; its Way is therefore devoid of sound to be heard.)