Histories
Herodotus
Herodotus. Godley, Alfred Denis, translator. Cambridge, MA; London: Harvard University Press; William Heinemann, Ltd., 1920-1925 (printing).
Those allies who were dismissed went off in obedience to Leonidas, only the Thespians and Thebans remaining with the Lacedaemonians. The Thebans remained against their will and desire, for Leonidas kept them as hostages. The Thespians very gladly remained, saying they would not abandon Leonidas and those with him by leaving; instead they would stay and die with them. Their general was Demophilus son of Diadromes.
Xerxes made libations at sunrise and waiting till about mid-morning, made his assault. Epialtes had advised this, for the descent from the mountain is more direct, and the way is much shorter than the circuit and ascent.
Xerxes and his barbarians attacked, but Leonidas and his Hellenes, knowing they were going to their deaths, advanced now much farther than before into the wider part of the pass. In all the previous days they had sallied out into the narrow way and fought there, guarding the defensive wall.