Hesiod, Shield of Heracles

“Hail, offspring of far-famed Lynceus! Even now Zeus who reigns over the blessed gods gives you power to slay Cycnus and to strip off his splendid armor. [330] Yet I will tell you something besides, mightiest of the people. When you have robbed Cycnus of sweet life, then leave him there and his armor also, and you yourself watch man-slaying Ares narrowly as he attacks, and wherever you shall see him uncovered below his cunningly-wrought shield, [335] there wound him with your sharp spear. Then draw back; for it is not ordained that you should take his horses or his splendid armor.” So said the bright-eyed goddess and swiftly got up into the car with victory and renown in her hands. [340] Then heaven-nurtured Iolaus called terribly to the horses, and at his cry they swiftly whirled the fleet chariot along, raising dust from the plain; for the goddess bright-eyed Athena put mettle into them by shaking her aegis. And the earth groaned all round them. [345] And they, horse-taming Cycnus and Ares, insatiable in war, came on together like fire or whirlwind. Then their horses neighed shrilly, face to face; and the echo was shivered all round them. And mighty Heracles spoke first and said to that other: [350] “Cycnus, my friend! Why do you set your swift horses at us, men who are tried in labor and pain? No, guide your fleet car aside and yield and go out of the path. It is to Trachis I am driving on, to Ceyx the king, who is the first in Trachis for power and for honor, [355] and that you yourself know well, for you have his daughter dark-eyed Themistinoe to wife. Fool! For Ares shall not deliver you from the end of death, if we two meet together in battle. Another time ere this I declare he has made trial [360] of my spear, when he defended sandy Pylos and stood against me, fiercely longing for fight. Thrice was he stricken by my spear and dashed to earth, and his shield was pierced; but the fourth time I struck his thigh, laying on with all my strength, and tore deep into his flesh.