The original quotation is found in the biography of Caius Julius
Caesar the Dictator (ca.100-44 B.C.) by the Silver Age Roman author
Caius Suetonius Tranquillus. Caesar, having exhausted all political
compromises by which he might have returned to Rome without risk,
decided that his only safety lay in civil war. However, realizing the
perils and the ruin that this would bring, he paused at the border of
Italy and Gaul, his assigned province, before taking the fatal step.
When finally he had made up his mind to enter Italy with his army, he
declared, "Jacta alea est, "the die is cast."
Entry for Caius Julius Caesar, 1911 Encyclopaedia Britannica
'But in 54 B.C. Julia, the daughter of Caesar and wife of Pompey,
died, and in 53 B.C. Crassus was killed at Carrhae. Pompey now drifted
apart from Caesar and became the champion of the senate. In 52 B.C. he
passed a fresh law de jure magistratuum which cut away the ground
beneath Caesars feet by making it possible to provide a successor to
the Gallic provinces before the close of 9 B.C., which meant that
Caesar would become for some months a private person, and thus liable
to be called to account for his unconstitutional acts. Caesar had no
resource left but uncompromising obstruction, which he sustained by
enormous bribes. His representative in 50 B.C., the tribune C.
Scribonius Curio, served him well, and induced the lukewarm majority
of the senate to refrain from extreme measures, insisting that Pompey,
as well as Caesar, should resign the imperium. But all attempts at
negotiation failed, and in January 49 B.C., martial law having been
proclaimed on the proposal of the consuls, the tribunes Antony and
Cassius fled to Caesar, who crossed the Rubicori (the frontier of
Italy) with a single legion, exclaiming Alea jacta est.'
C. Suetonius Tranquillus (A.D. 75-ca.-140)
De Vita Caesarum, Divus Julius, Latin text
" Cum ergo sublatam tribunorum intercessionem ipsosque urbe
cessisse nuntiatum esset, praemissis confestim clam cohortibus, ne qua
suspicio moueretur, et spectaculo publico per dissimulationem
interfuit et formam, qua ludum gladiatorium erat aedificaturus,
considerauit et ex consuetudine conuiuio se frequenti dedit. dein post
solis occasum mulis e proximo pistrino ad uehiculum iunctis
occultissimum iter modico comitatu ingressus est; et cum luminibus
extinctis decessisset uia, diu errabundus tandem ad lucem duce reperto
per angustissimos tramites pedibus euasit. consecutusque cohortis ad
Rubiconem flumen, qui prouinciae eius finis erat, paulum constitit, ac
reputans quantum moliretur, conuersus ad proximos: 'etiam nunc,'
inquit, 'regredi possumus; quod si ponticulum transierimus, omnia
armis agenda erunt.'
 Cunctanti ostentum tale factum est. quidam eximia magnitudine et
forma in proximo sedens repente apparuit harundine canens; ad quem
audiendum cum praeter pastores plurimi etiam ex stationibus milites
concurrissent interque eos et aeneatores, rapta ab uno tuba prosiliuit
ad flumen et ingenti spiritu classicum exorsus pertendit ad alteram
ripam. tunc Caesar: 'eatur,' inquit, 'quo deorum ostenta et inimicorum
 Iacta alea est,' inquit. atque ita traiecto exercitu, adhibitis
tribunis plebis, qui pulsi superuenerant, pro contione fidem militum
flens ac ueste a pectore discissa inuocauit. existimatur etiam
equestres census pollicitus singulis; quod accidit opinione falsa. nam
cum in adloquendo adhortandoque saepius digitum laeuae manus ostentans
adfirmaret se ad satis faciendum omnibus, per quos dignitatem suam
defensurus esset, anulum quoque aequo animo detracturum sibi, extrema
contio, cui facilius erat uidere contionantem quam audire, pro dicto
accepit, quod uisu suspicabatur; promissumque ius anulorum cum milibus
quadringenis fama distulit."
English translation, J.C. Rolfe (Loeb Classical Library, Harvard
Universiy Press, 1913)
Ancient History Sourcebook e-text:
"XXXI. [49 B.C.] Accordingly, when word came that the veto of the
tribunes had been set aside and they themselves had left the city, he
at once sent on a few cohorts with all secrecy, and then, to disarm
suspicion, concealed his purpose by appearing at a public show,
inspecting the plans of a gladiatorial school which he intended
building, and joining as usual in a banquet with a large company. It
was not until after sunset that he set out very privily with a small
company, taking the mules from a bakeshop hard by and harnessing them
to a carriage; and when his lights went out and he lost his way, he
was astray for some time, but at last found a guide at dawn and got
back to the road on foot by narrow bypaths. Then, overtaking his
cohorts at the river Rubicon, which was the boundary of his province,
he paused for a while, and realizing what a step he was taking, he
turned to those about him and said: 'Even yet we may draw back; but
once cross yon little bridge, and the whole issue is with the sword."
XXXII. As he stood in doubt, this sign was given him. On a sudden
there appeared hard by a being of wondrous stature and beauty, who sat
and played upon a reed; and when not only the shepherds flocked to
hear him, but many of the soldiers left their posts, and among them
some of the trumpeters, the apparition snatched a trumpet from one of
them, rushed to the river, and sounding the war-note with mighty
blast, strode to the opposite bank. Then Caesar cried: " Take we the
course which the signs of the gods and the false dealing of our foes
point out. The die is cast [Iacta alea est,' inquit'].
XXXIII. Accordingly, crossing with his army, and welcoming the
tribunes of the plebeians, who had come to him after being driven
from Rome, he harangued the soldiers with tears, and rending his robe
from his breast besought their faithful service. It is even thought
that he promised every man the estate of an eques, but that came of a
misunderstanding; for since he often pointed to the finger of his left
hand as he addressed them and urged them on, declaring that to satisfy
all those who helped him to defend his honor he would gladly tear his
very ring from his hand, those on the edge of the assembly, who could
see him better than they could hear his words, assumed that he said
what his gesture seemed to mean; and so the report went about that he
had promised them the right of the ring and four hundred thousand
sesterces as well."
This appears to be a garbled paraphrase of "Macbeth", Act V, Scene V ,
by William Shakespeare.
16B. The Queen, my lord, is dead.
16B. She should have died hereafter.
17. There would have been a time for such a word.
18. Tomorrow, and tomorrow, and tomorrow
19. Creeps in this petty pace from day to day
20. To the last syllable of recorded time,
21. And all our yesterdays have lighted fools
22. The way to dusty death. Out, out, brief candle.
23. Life's but a walking shadow, a poor player
24. That struts and frets his hour upon the stage,
25. And then is heard no more. It is a tale
26. Told by an idiot, full of sound and fury,
27B. Signifying nothing.
No search strategy. General knowledge.
Finding the references.
Suetonius Julius Caesar text
Macbeth Act V "Tomorrow, and tomorrow, and tomorrow"