"Then stretched I forth my hand a little forward"

(Canto 13, line 34)

Here Dante again follows Virgil in the Aeneid, book 3. It tells how Polydorus, youngest son of the Trojan ruler Priam, was unrightfully killed by Polymester and buried on the Thracian shore. When Aeneas came ashore there, he broke some branches for making a sacrifice, and saw the branches started spouting blood while a voice from the grave urged him to leave quickly.