Quintus Curtius Rufus, History of Alexander 8.12.8

8.12.8

Ac primo Alexander non socium, sed hostem adventare credebat iamque et ipse arma milites capere et equites discedere in cornua iusserat paratus ad pugnam. At Indus cognito Macedonum errore iussis subsistere ceteris ipse concitat equum, quo vehebatur: idem Alexander quoque fecit, sive hostis sive amicus occurreret, vel sua virtute vel illius fide tutus.

Alexander at first thought it was not a friendly but a hostile army that approached, and had already ordered the soldiers to arm themselves, and the cavalry to divide to the wings, and was ready for action. But the Indian prince, on seeing the mistake of the Macedonians, put his horse to the gallop, leaving orders that no one else was to stir from his place. Alexander likewise galloped forward, not knowing whether it was an enemy or a friend he had to encounter, but trusting for safety perhaps to his valour, perhaps to the other's good faith. They met in a friendly spirit, as far as could be gathered from the expression of each one's face, but from the want of an interpreter to converse was impossible. An interpreter was therefore procured, and then the barbarian prince explained that he had come with his army to meet Alexander that he might at once place at his disposal all the forces of his empire, without waiting to tender his allegiance through deputies. He surrendered, he said, his person and his kingdom to a man who, as he knew, was fighting not more for fame than fearing to incur the reproach of perfidy.