Eliot's note for line 427

V. Purgatorio, XXVI, 148.

«Ara vos prec, per aquella valor
que vos guida al som de l'escalina,
sovenha vos a temps de ma dolor!».
Poi s'ascose nel foco che li affina.

Commentator's note

Eliot is referring us to Dante Alighieri's poem Purgatorio, Canto XXVI verse 148

The lines quoted by Eliot can be translated as:

'And so I pray you, by that virtue
which guides you to the top of the stair,
be reminded in time of my pain.'
Then he hid himself in the fire that purifies them.