Commentary Inf VI 25-27

The 'sop' to Cerberus, in Virgil a honeyed cake (Aen. VI.419-422), here becomes mere earth (terra). Kleinhenz (Klei.1975.1), p. 190, has pointed out that Dante's strategic redoing of Virgil has its biblical resonance, as God's malediction of the serpent (Genesis 3:14) concludes '... terram comedes cunctis diebus vitae tuae' (and dust shall you eat all the days of your life). The serpent's punishment for having urged Eve to eat the fruit of the tree is himself to eat the dead earth; his punishment is shared now by Cerberus.