Commentary Purg XXII 140-141

Like the tree, the voice from within it is mysterious as well; it would rather seem to be the 'voice' of the tree itself than anything else.  What the voice says at first may seem to be a version of God's prohibition of the fruit of the Tree of the Knowledge of Good and Evil to Adam (Genesis 2:17), a passage Mattalia [DDP Mattalia.Purg.XXII.141] believes is repeated at [Purg XXIV 115] -- but see C.Purg.XXIV.115.  However, it seems far more likely that this voice speaks of the result of Original Sin, humankind's loss of eternal life, symbolized here in the unavailability of the fruit (described in C.Purg.XXII.132) of this tree, the Tree of Life.