Titus Livius (Livy), The History of Rome, Book 24
Frank Gardener Moore, Professor Emeritus in Columbia University, Ed.

15. On the next day, when the signals began to sound, these soldiers were the first of all to assemble at headquarters, ready and in formation. After sunrise Gracchus led his troops out into line, and the enemy did not delay the battle. [2] They had seventeen thousand infantry, mostly Bruttians and Lucanians, twelve hundred cavalry, among them very few [p. 221]Italians, nearly all the rest Numidians and Mauri.¹ The battle was fierce and long; for four hours it did not incline either way. [3] And nothing hampered the Romans more than that enemies' heads were made the price of freedom. For when a man had boldly slain an enemy, in the first place he was wasting time in cutting off the head with difficulty in the confusion and turmoil; [4] and then, as his right hand was occupied in holding the head, the bravest had ceased to be fighters, while the battle was turned over to the spiritless and the fearful. [5] When the tribunes of the soldiers reported' this to Gracchus: that they were not wounding a single enemy standing, but butchering the fallen; and that in the soldier's right hands there were human heads instead of swords, he ordered the command at once given that they should throw away the heads and attack the enemy. [6] Their courage, he said, was sufficiently clear and conspicuous, and for active men freedom would be beyond a doubt. Thereupon the battle Was renewed, and the cavalry also charged the enemy. [7] Since the Numidians met this charge gallantly and the cavalry battle was no less spirited than that of the infantry, the issue was for the second time made doubtful. While the commanders on both sides heaped abuse, the Roman on the Bruttians and Lucanians, so many times defeated and subdued by their ancestors, the Carthaginian on the Roman slaves and prison-house [8??] .soldiers, Gracchus finally declared that they had no reason to hope for freedom, unless on that day the enemy should-be routed and put to flight.