Passage 4.29.12
Φιλοποίμενος δὲ σὺν ἱππεῦσιν ὀλίγοις ἀφικομένου πολὺ ὕστερον ἢ ὁ μετὰ Λυκόρτα στρατός, πυθέσθαι δὲ οὐδέν πω τῶν ἐς αὐτοὺς δεδυνημένου, νικῶσιν οἱ Μεσσήνιοι γινομένης σφίσιν ἐξ ὑπερδεξίων τῆς μάχης καὶ ζῶντα αἱροῦσι Φιλοποίμενα. τρόπον δὲ ὅντινα ὁ Φιλοποίμην ἑάλω καὶ ὡς ἐτελεύτησε, τάδε μὲν ἡμῖν καὶ ὕστερον ὁ Ἀρκαδικὸς λόγος ἐπέξεισι· Μεσσηνίων δὲ οἵ τε Φιλοποίμενι αἴτιοι τῆς τελευτῆς ἔδοσαν δίκας καὶ ἡ Μεσσήνη συνετέλεσεν αὖθις ἐς τὸ Ἀχαϊκόν.
Philopoemen came much later with a few horsemen, after the army led by Lycortas had already arrived; before he had learned anything of what had befallen them, the Messenians were victorious on their side of the battlefield, which was on their right wing, and they captured Philopoemen alive. By what manner Philopoemen was captured and how he died, I shall relate further, when I later discuss Arcadian traditions. However, the Messenians who were responsible for the death of Philopoemen subsequently paid the penalty, and Messene itself afterward rejoined the Achaean League.