Commentary Par XXV 7

  altra voce... altro vello: lit., deeper voice and facial hair or gray hair (see Dante’s first eclogue (Egl.I.42-44) of the mature man; metaphorically, with prophetic speech and this book, written on vellum (?); in addition, new 'golden fleece' (see Metam. VI.720: 'vellera,' and Dante, in Egl.II.1: 'Velleribus Colchis' [Colchian fleece]) -- Dante as Jason (cf. [Par II 16-18]; [Par XXXIII 94-96]).

See Velli (Vell.1989.1), pp. 36-38, for the possible echo in Dante's voce and vello of Statius's use of these two words in Thebaid II.96.