Passage 10.23.1
Βρέννῳ δὲ καὶ τῇ στρατιᾷ τῶν τε Ἑλλήνων οἱ ἐς Δελφοὺς ἀθροισθέντες ἀντετάξαντο, καὶ τοῖς βαρβάροις ἀντεσήμαινε τὰ ἐκ τοῦ θεοῦ ταχύ τε καὶ ὧν ἴσμεν φανερώτατα. ἥ τε γὰρ γῆ πᾶσα, ὅσην ἐπεῖχεν ἡ τῶν Γαλατῶν στρατιά, βιαίως καὶ ἐπὶ πλεῖστον ἐσείετο τῆς ἡμέρας, βρονταί τε καὶ κεραυνοὶ συνεχεῖς ἐγίνοντο·
Against Brennus and his army, the Greeks who had gathered at Delphi arranged themselves in opposition, and the divine signs opposing the foreigners manifested swiftly and most clearly, according to our knowledge. For the whole earth occupied by the army of the Gauls shook violently and continuously for much of the day, while thunderbolts and lightning repeatedly struck.