Commentary Purg X 34-45

The first example of each virtue (here Humility), opposed to the capital vice purged on each of the seven terraces, is always Mary.  These four tercets are spare and central in their presentation of the Annunciation: only Gabriel and Mary are seen, minus the 'background' expected by any medieval reader, familiar with the iconography of this moment: dove, ray of light, garden, etc.  As the Ottimo (DDP Ottimo.Purg.X.34-44) has it, the 'long-standing ban' had been in effect since the time recorded in Genesis 3 (the Fall) and was only rescinded when Christ harrowed hell.

      The sculpted forms are so vivid that they actually seem to speak.  Thus does Dante recast the key spoken moments of Luke (1:26-38), Gabriel's charge and Mary's humble acceptance of it.

      As for a tradition of renditions of 'visible speech' in painting see Fengler and Stephany (Feng.1977.1), p. 132: Simone Martini's Uffizi Annunciation (1333 -- but reflecting a pre-existent tradition), where the angel's words are depicted on a horizontal line on the painting's gold background.