Hesiod, Shield of Heracles

“O hero Iolaus, best beloved of all men, truly Amphitryon sinned deeply against the blessed gods who dwell on Olympus [80] when he came to sweet-crowned Thebes and left Tiryns, the well-built citadel, because he slew Electryon for the sake of his wide-browed oxen. Then he came to Creon and long-robed Eniocha, who received him kindly and gave him all fitting things, [85] as is due to suppliants, and honored him in their hearts even more. And he lived joyfully with his wife the neat-ankled daughter of Electryon: and presently, while the years rolled on, we were born, unlike in body as in mind, even your father and I. From him Zeus took away sense, so that he left his home and his parents [90] and went to do honor to the wicked Eurystheus—unhappy man! Deeply indeed did he grieve afterwards in bearing the burden of his own mad folly; but that cannot be taken back. But on me fate laid heavy tasks. [95] “Yet, come, friend, quickly take the red-dyed reins of the swift horses and raise high courage in your heart and guide the swift chariot and strong fleet-footed horses straight on. Have no secret fear at the noise of man-slaying Ares who now rages shouting about the holy grove [100] of Phoebus Apollo, the lord who shoots from afar. Surely, strong though he be, he will have enough of war.” And blameless Iolaus answered him again: “Good friend, truly the father of men and gods greatly honors your head and the bull-like Earth-Shaker also, [105] who keeps Thebe's veil of walls and guards the city,—so great and strong is this fellow they bring into your hands that you may win great glory. But come, put on your arms of war that with all speed we may bring the car of Ares and our own together and [110] fight; for he shall not frighten the dauntless son of Zeus, nor yet the son of Iphiclus: rather I think he will flee before the two sons of blameless Alcides who are near him and eager to raise the war cry for battle; for this they love better than a feast.”