Hesiod, The Homeric Hymns, and Homerica
Page: 66(ll. 27-55) But the father of men and gods was forming another scheme in his heart, to beget one to defend against destruction gods and men who eat bread. So he arose from Olympus by night pondering guile in the deep of his heart, and yearned for the love of the well-girded woman. Quickly he came to Typhaonium, and from there again wise Zeus went on and trod the highest peak of Phicium 1801: there he sat and planned marvellous things in his heart. So in one night Zeus shared the bed and love of the neat-ankled daughter of Electyron and fulfilled his desire; and in the same night Amphitryon, gatherer of the people, the glorious hero, came to his house when he had ended his great task. He hastened not to go to his bondmen and shepherds afield, but first went in unto his wife: such desire took hold on the shepherd of the people. And as a man who has escaped joyfully from misery, whether of sore disease or cruel bondage, so then did Amphitryon, when he had wound up all his heavy task, come glad and welcome to his home. And all night long he lay with his modest wife, delighting in the gifts of golden Aphrodite. And she, being subject in love to a god and to a man exceeding goodly, brought forth twin sons in seven-gated Thebe. Though they were brothers, these were not of one spirit; for one was weaker but the other a far better man, one terrible and strong, the mighty Heracles. Him she bare through the embrace of the son of Cronos lord of dark clouds and the other, Iphiclus, of Amphitryon the spear-wielder—offspring distinct, this one of union with a mortal man, but that other of union with Zeus, leader of all the gods.
(ll. 57-77) And he slew Cycnus, the gallant son of Ares. For he found him in the close of far-shooting Apollo, him and his father Ares, never sated with war. Their armour shone like a flame of blazing fire as they two stood in their car: their swift horses struck the earth and pawed it with their hoofs, and the dust rose like smoke about them, pounded by the chariot wheels and the horses' hoofs, while the well-made chariot and its rails rattled around them as the horses plunged. And blameless Cycnus was glad, for he looked to slay the warlike son of Zeus and his charioteer with the sword, and to strip off their splendid armour. But Phoebus Apollo would not listen to his vaunts, for he himself had stirred up mighty Heracles against him. And all the grove and altar of Pagasaean Apollo flamed because of the dread god and because of his arms; for his eyes flashed as with fire. What mortal men would have dared to meet him face to face save Heracles and glorious Iolaus? For great was their strength and unconquerable were the arms which grew from their shoulders on their strong limbs. Then Heracles spake to his charioteer strong Iolaus: