Dante 5

In Songs of Experience Blake introduced the 'forest';

TIGER, tiger, burning bright
In the forests of the night, Through the years of his career he used 'forest' often; it occurred 63 times in his poetry. In his last years he turned to the poetry of Dante and found his 'forest' and put it in one of his Illustrations.

Dante and Virgil Penetrate the Forest
Blake's Illustration
Wiki Common

Dante speaks from Dante's Inferno II:
"Now go, for both of us have one will; thou guide. thou lord and master," 
Thus I spoke to him,and he proceeding, I entered on the arduous and savage way.

From notes by Milton Klonsky's Blake's Dante:
Page 187: Virgil strides forward with his right foot and flings up his arms like the forks of  the oak trees twisting around and directing the poets deeper into the forest.

From Blake's Milton, Plate 25  (Erdman 123):

And in the City of Golgonooza: & in Luban: & around  The Lake of Udan-Adan, in the 

Forests of Entuthon Benython:

Where Souls incessant wail, being piteous Passions & Desires, With neither lineament nor form: but like to wat'ry clouds