Passage 9.5.12
Πολυνείκης δὲ περιόντος μὲν καὶ ἄρχοντος Οἰδίποδος ὑπεξῆλθεν ἐκ Θηβῶν δέει μὴ τελεσθεῖεν ἐπὶ σφίσιν αἱ κατᾶραι τοῦ πατρός· ἀφικόμενος δὲ ἐς Ἄργος καὶ θυγατέρα Ἀδράστου λαβὼν κατῆλθεν ἐς Θήβας μετάπεμπτος ὑπὸ Ἐτεοκλέους μετὰ τὴν τελευτὴν Οἰδίποδος. κατελθὼν δὲ ἐς διαφορὰν προήχθη τῷ Ἐτεοκλεῖ, καὶ οὕτω τὸ δεύτερον ἔφυγε· δεηθεὶς δὲ Ἀδράστου δοῦναί οἱ δύναμιν τὴν κατάξουσαν, τήν τε στρατιὰν ἀπόλλυσι καὶ πρὸς τὸν Ἐτεοκλέα αὐτὸς μονομαχεῖ κατὰ πρόκλησιν.
Polyneices, while Oedipus was still alive and ruling, departed from Thebes for fear that his father's curses might be fulfilled upon him. Coming to Argos and having taken Adrastus' daughter in marriage, he returned to Thebes when summoned by Eteocles following Oedipus' death. Upon his return, however, he became embroiled in a dispute with Eteocles, and thus fled a second time. After beseeching Adrastus to grant him an army that would restore him, he lost the host and himself engaged Eteocles in single combat, according to a mutual challenge.