Hesiod, Shield of Heracles

Or like her who left home and country and came to Thebes, following warlike Amphitryon,—even Alcmena, the daughter of Electryon, gatherer of the people. She surpassed the tribe of womankind [5] in beauty and in height; and in wisdom none vied with her of those whom mortal women bore of union with mortal men. Her face and her dark eyes wafted such charm as comes from golden Aphrodite. And she so honored her husband in her heart [10] as none of womankind did before her. In truth he had slain her noble father violently when he was angry about oxen; so he left his own country and came to Thebes and was suppliant to the shield-carrying men of Cadmus. There he dwelt with his modest wife [15] without the joys of love, nor might he go in unto the neat-ankled daughter of Electryon until he had avenged the death of his wife's great-hearted brothers and utterly burned with blazing fire the villages of the heroes, the Taphians and Teleboans; [20] for this thing was laid upon him, and the gods were witnesses to it. And he feared their anger, and hastened to perform the great task to which Zeus had bound him. With him went the horse-driving Boeotians, breathing above their shields, [25] and the Locrians who fight hand to hand, and the gallant Phocians eager for war and battle. And the noble son of Alcaeus led them, rejoicing in his host. 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. [30] 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:¹ there he sat and planned marvellous things in his heart. [35] So in one night Zeus shared the bed and love of the neat-ankled daughter of Electryon 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.