大般涅槃經疏 33.5

33.5

「犢子梵志」下，第七外道，文為三：一緣起、二論義、三歸伏。亦以默然為緣起者，不得例前表其儒雅，是故徐詳待三方答。「犢子言」下，二是論義。此無自執但咨正義，故因佛默先問默意。次佛思默意，乃開問端。

From "The Vātsīputrīya brahmacārin" onward is the seventh non-Buddhist [ascetic]. The text has three [parts]: first, the circumstances of origin; second, the debate on doctrines; third, submission. That silence is also taken as the circumstance of origin cannot be compared to the previous instance indicating scholarly refinement; therefore, [the Buddha] deliberated deliberately and waited until [asked] three times before replying. From "The Vātsīputrīya said" onward is the second [part], the debate on doctrines. Here, he has no personal dogmatism, but merely inquires about the correct doctrine; hence, relying on the Buddha's silence, he first asks about the meaning of the silence. Next, the Buddha reflects upon the meaning of the silence, and thereupon opens the opening for questioning.