According to Plutarch, Caesar uttered the famous phrase in Greek:
'And now word was brought that Caesar had seized Ariminum, a large city of Italy, and was marching directly upon Rome with all his forces. But this was false. For he was marching with no more than three hundred horsemen and five thousand men-at‑arms; the rest of his forces were beyond the Alps, and he did not wait for them, since he wished to fall upon his enemies suddenly, when they were in confusion and did not expect him, rather than to give them time and fight them after they were prepared. And so, when he was come to the river Rubicon, which was the boundary of the province allotted to him, he stood in silence and delayed to cross, reasoning with himself, of course, upon the magnitude of his adventure. Then, like one who casts himself from a precipice into a yawning abyss, he closed the eyes of reason and put a veil between them and his peril, and calling out in Greek to the bystanders these words only, "Let the die be cast," he set his army across'.
-Plutarch, Life of Pompey, 60