俱舍論記 16.26

16.26

「以阿羅漢至永寂靜故」者，答。以阿羅漢是實牟尼，諸煩惱言永寂靜故，非有學等。煩惱如言喧雜，名煩惱言。又解：煩惱如言相似，言謂言諍，煩惱謂煩惱諍，名煩惱言。又解：煩惱緣言起，故名煩惱言。雖有煩惱亦不緣言，此中且據緣言起說。

Regarding "Because an arhat... is eternally tranquil": This is the answer. Because an arhat is a real muni, and the speech of defilements is eternally tranquil—not so for the śaikṣa and others. Defilements are noisy and clamorous like speech; hence they are called "the speech of defilements". Another explanation: defilements resemble speech; "speech" refers to verbal disputes, and "defilement" refers to defilement disputes, hence called "the speech of defilements". Another explanation: defilements arise conditioned by speech; hence they are called "the speech of defilements". Although there are defilements that do not take speech as their condition, here it is stated provisionally based on those that arise conditioned by speech.