But when Heracles had made the circuit of the Adriatic, and had journeyed around the gulf on foot, he came to Epirus, whence he made his way to Peloponnesus. And now that he had performed the tenth Labour he received a Command from Eurystheus to bring Cerberus up from Hades to the light of day. And assuming that it would be to his advantage for the accomplishment of this Labour, he went to Athens and took part in the Eleusinian Mysteries, Musaeus, the son of Orpheus, being at that time in charge of the initiatory rites.
[...]
Heracles, then, according to the myths which have come down to us, descended into the realm of Hades, and being welcomed like a brother by Persephonê brought Theseus and Peirithoüs back to the upper world after freeing them from their bonds. This he accomplished by the favour of Persephonê, and receiving the dog Cerberus in chains he carried him away to the amazement of all and exhibited him to men.
- Diodorus Siculus, Library of History, Book 4
Indeed, he often lapses unawares into the manner of Xenarchus, as, for instance, when he says he thinks it was a bad omen for the Athenians that Nicias, whose name was derived from victory, declined at first to head their expedition; also that, by the mutilation of the "Hermae," Heaven indicated to them in advance that by the hands of Hermocrates the son of Hermon they were to suffer most of their reverses during the war; and, further, that it was fitting that Heracles should aid the Syracusans, for the sake of their goddess Cora [Persephone], who delivered Cerberus into his hands, but should be angry with the Athenians, because they were trying to succour the Egestaeans, although they were descendants of the Trojans, whose city he had once destroyed because of wrong done him by Laomedon their king.
- Plutarch, Lives, The Life of Nicias