Both points of view are found in Cicero’s review of the events of January written to Tiro on the twenty-seventh:
Maximam autem plagam accepit quod is qui summum auctoritatem in illius exercutu habebat, T. Labienus, socius scleris esse noluit, reliquit illum et est nobiscum. . .;
Caesar received, however, a very great blow because that man who held the highest position in his army, T. Labienus, refused to be an ally in his crime and left him and is now with us (Cic. Fam 16.12.4).
The question remains why Labienus left Caesar. His departure did not take Caesar unaware. He had one legion in Cisalpine Gaul, and that was split into cohorts and scattered in municipia and in a province fervently Caesarian.[33] How sincerely Caesar contemplated a consulship with him is unanswerable. But Caesar’s letters to Cicero before the latter joined Pompey in Greece demonstrate his appreciation for appearances.[34] The governorship provided his enemies with a token of his goodwill and Labienus with a harmless opportunity to disclose his intentions.[35] Afterwards, Caesar sent Labienus his money and baggage with that same contemptuous indifference with which he returned to Domitius the war funds left behind at Corfinium.[36]
Whatever Labienus’ reasons, they clearly were more concerned with leaving Caesar than with joining his enemies. What may have been the rumor current at Rome in January 49 is preserved in Dio: jealousy and resentment turned into hatred.[37] Of the hatred there can be little doubt: