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

23. Rejoicing at this vision, he led his troops across the Ebro in three columns, after sending agents ahead, to win over with presents the Gauls who dwelt in the region which the army had to cross, and to explore the passes of the Alps. [2] He had ninety thousand foot and twelve thousand horse [p. 67]when he crossed the Ebro. He now subdued the¹ Ilergetes, and the Bargusii and Ausetani, and also Lacetania, which lies at the foot of the Pyrenees. All this coast he put in charge of Hanno, that the passes connecting Spain and Gaul might be under his control. [3] To garrison this district, he gave Hanno ten thousand foot and a thousand horse.

[4] When the army had entered the defiles which lead over the Pyrenees, and more definite rumours had spread amongst the barbarians that the war was to be with Rome, three thousand of the Carpetanian foot turned back. It was understood that they were influenced not so much by the war as by the long march and the impossibility of crossing the Alps. [5] To recall them or to detain them forcibly would have been hazardous, for it might have roused resentment in the savage bosoms of the others. [6] And so Hannibal sent back to their homes above seven thousand more, whom he had perceived to be chafing at the service, pretending that he had also dismissed the Carpetani.