Titus Livius (Livy), The History of Rome, Book 25
Frank Gardener Moore, Professor Emeritus in Columbia University, Ed.

12. At Rome the consuls and praetors were detained by the Latin festival until the 26th of April. [2] After performing the rites on that day on the Mount,¹ each set out for his assignment. Then fresh religious scruples were aroused by the verses of Marcius. [3] A noted seer had been this Marcius, and when in the preceding year search was being made by decree of the senate for such books, they had come [p. 385]into the hands of Marcus Aemilius,² the praetor³ urbanus, who was in charge of the matter. He had immediately turned them over to the new praetor, Sulla. [4] Of the two prophecies⁴ of this Marcius the authority of one, made known after the event, was confirmed by the outcome and lent credibility to the other also, whose time had not yet come. [5] In the earlier prophecy the disaster at Cannae had been predicted in such terms as these: “Flee the river Canna, thou descendant of Troy, that foreigners may not compel thee to do battle in the Plain of Diomed. [6] But thou wilt not believe me until thou hast filled the plain with blood, and many thousands of thy slain will the river bear from the fruitful land down to the great sea. To fishes and birds and beasts that dwell on the land thy flesh shall be meat. For thus hath Jupiter declared to me.” [7] And those who had fought in that region recognized the plains of the Argive Diomed and the river Canna no less than the disaster itself. Then the second prophecy was read, being not only more obscure because the future is more uncertain [8??] than the past, but more difficult also in the way it was written. [9] “If you wish, Romans, to drive out enemies, the sore which has come from afar, I propose that a festival be vowed to Apollo, to be observed with good cheer in honour of Apollo every year. When the people shall have given a part out of the treasury, private citizens shall contribute on their own behalf and that of their families. [10] In charge of the conduct of that festival shall be the praetor who is then chief judge for the people and [p. 387]the commons. The decemvirs⁵ shall offer the victims⁶ according to Greek rite. If ye will do this rightly ye shall forever rejoice, and your state will change for the better. For that god who graciously nurtures your meadows will destroy your enemies.” For the interpretation of the prophecy they took one day. [11] On the next day the senate made a decree that in regard to the festival to be held and the sacrifices in honour of Apollo the decemvirs should consult the books.⁷ [12] Those passages having been consulted and reported to the senate, the fathers voted that a festival should be vowed and held in honour of Apollo, and after the festival had been held the sum of twelve thousand asses should be given to the praetor for the ceremonies, and two full-grown victims. [13] A second decree of the senate was made, that the decemvirs should offer sacrifice according to Greek rite and with these victims: to Apollo an ox with gilded horns and two white she-goats⁸ with gilded horns, to Latona a cow with gilded horns. [14] When the praetor was about to open the festival in the Circus Maximus, he ordered by edict that during that feast the people should make their contribution to Apollo according to their means. [15] Such is the origin of the festival of Apollo, vowed and kept to secure victory, not health, as most think. The people wore garlands at the spectacles, the matrons offered prayers, everybody feasted in the atrium with open doors, and the day was kept with every kind of ceremony.