成唯識論演祕 2.668

2.668

第三轉者名為由聲，亦名具聲，由智惠力斷惑所顯故屬由聲。更有餘義，如《因明鈔》。

The third case is called the instrumental case (karaṇa / hetu), also called the case of means; because it is manifested through the power of wisdom severing delusion, it belongs to the instrumental case. There are other interpretations, as in the Notes on Hetuvidyā.