Servius, Commentary on the Aeneid 3.14:
“This Lycurgus was the son of Dryas, the king of the race of the Thracian Bistones. As the story has it, he cut his own legs while contemptuously attempting to cut Dionysus’ vines. In truth, he abstained from drink, which is agreed to be a characteristic of a harsh nature, and is even said about Demosthenes. But as other people say, Lycurgus, being vexed that Dionysus was cultivated by other races and learning that he had entered Thrace with his band of followers, lashed some of the Bacchants whom he captured with rods, and began to pursue Dionysus himself with the aim of killing him. But after Dionysus hurled himself into the sea to escape Lycurgus and was taken in and set free by the nymph Thetis, Lycurgus began to cut his vines; in so doing, through the madness visited upon him by the gods, he actually cut his own legs.”
Lycurgus autem hic filius Dryantis, rex gentis Bistonum Thraciae fuit: qui ut habet fabula, dum contempnens Liberum eius amputat vites, crura sua incidit. re vera autem abstemius fuit: quos constat acrioris esse naturae, quod etiam de Demosthene dictum est. Lycurgus vero, ut alii dicunt, cum indignaretur Liberum ab omnibus gentibus coli, ut primum eum Thraciae fines cum suo comitatu introisse cognovit, comprehensas Bacchas eius flagellis verberavit, ipsum vero insequi, ut occideret, coepit. sed postquam se Liber fugiens ut evaderet praecipitavit in mare et a Thetide nympha exceptus liberatusque est, Lycurgus vites eius amputare coepit: quapropter per furorem a diis inmissum ipse sibi crura succidit.