Titus Livius (Livy), The History of Rome, Book 21
Benjamin Oliver Foster, Ph.D., Ed.

22. And considering that neither must Spain be neglected, and so much the less since he was not unaware that Roman ambassadors had journeyed through it to seek the support of its leading men, he appointed it to be the charge of his brother Hasdrubal —an [2] active, energetic man —and secured it with troops, for the most part African. Of infantry there were eleven thousand eight hundred and fifty Africans, three hundred Ligurians, and five hundred Baliares. [3] To these infantry forces he added the following units of cavalry: four hundred and fifty Libyphoenicians —a race of mixed Punic and African blood —and some eight hundred Numidians and Moors, who dwell near the ocean,¹ and a little company of three hundred Spanish Ilergetes. Finally, that no sort of land force might be lacking, there were twenty-one elephants. [4] He also assigned a fleet to Spain, for the protection of its seaboard, since it might be expected that the Romans would [p. 65]again on this occasion employ that mode of warfare² in which they had been victorious. There were fifty quinqueremes, two quadriremes, and five triremes. But only thirty-two quinqueremes and the five triremes were equipped and manned with rowers.³

From Gades Hannibal returned to New Carthage, to the winter quarters of his army. [5] Setting out from thence, he marched along the coast, past the city of Onusa, to the Ebro. [6] It was there, as they tell, that he saw in his sleep a youth of godlike aspect, who declared that he was sent by Jupiter to lead him into Italy: let him follow, therefore, nor anywhere turn his eyes away from his guide. [7] At first he was afraid and followed, neither looking to the right nor to the left, nor yet behind him; but presently wondering, with that curiosity to which all of us are prone, what it could be that he had been forbidden to look back upon, he was unable to command his eyes; [8] then he saw behind him a serpent of monstrous size, that moved along with vast destruction of trees and underbrush, and a storm-cloud coming after, with loud claps of thunder; [9] and, on his asking what this prodigious portent was, he was told that it was the devastation of Italy: he was therefore to go on, nor enquire further, but suffer destiny to be wrapped in darkness.