Passage 9.13.3
ὡς δὲ ὁ Λακεδαιμονίων καὶ Θηβαίων ἐξῆρτο ἤδη πόλεμος καὶ οἱ Λακεδαιμόνιοι δυνάμει καὶ αὑτῶν καὶ τῶν συμμάχων ἐπὶ τοὺς Θηβαίους ᾔεσαν, Ἐπαμινώνδας μὲν ἔχων τοῦ στρατοῦ μοῖραν ἀντεκάθητο ὑπὲρ τῆς Κηφισίδος λίμνης ὡς ποιησομένων ταύτῃ Πελοποννησίων τὴν ἐσβολήν, Κλεόμβροτος δὲ ὁ Λακεδαιμονίων βασιλεὺς ἐπὶ Ἀμβρόσσου τρέπεται τῆς Φωκέων· ἀποκτείνας δὲ Χαιρέαν, ὃς φυλάσσειν διετέτακτο τὰς παρόδους, καὶ ἄλλους τοὺς σὺν αὐτῷ Θηβαίους, ὑπερέβη καὶ ἐς Λεῦκτρα ἀφικνεῖται τὰ Βοιώτια.
When war now had broken out between the Lacedaemonians and Thebans, the Lacedaemonians advanced against the Thebans with the full force of themselves and their allies. Epaminondas, having a part of the army, took up a position by Lake Cephisis, in the expectation that the Peloponnesians would invade through that region. Cleombrotus, the Lacedaemonian king, however, turned towards Ambrossus, a city belonging to the Phocians. After killing Chaereas, who had been assigned to guard the passes, along with the other Thebans who were with him, he passed through and arrived in Leuctra, in the territory of Boeotia.