Commentary Purg XIII 141

Dante's locution is noteworthy in that it recapitulates exactly what Virgil had said describing Brutus in [Inf XXXIV 66]: 'e non fa motto.'  Perhaps one should not make too much of this, since other versions of the phrase occur variously through the poem: [Inf IX 101], [Inf XIX 48], [Inf XXXIII 48], [Purg II 25], [Purg V 7], [Purg VII 78].