Passage 4.28.2
Μεσσήνιοι δὲ αὐτοί τε μετὰ Ἀργείων καὶ Ἀρκάδων ἀντεῖχον τῷ πολέμῳ καὶ Ἀθηναίων ἀμῦναί σφισιν ἐδεήθησαν· οἱ δὲ ἐς μὲν τὴν Λακωνικὴν οὔποτε μετὰ ἐκείνων ἐσβαλεῖν ἔφασαν, ἀρχόντων δὲ Λακεδαιμονίων πολέμου καὶ ἐπιστρατευόντων τῇ Μεσσηνίᾳ παρέσεσθαι καὶ αὐτοί σφισιν ἐπηγγέλλοντο. τέλος δὲ οἱ Μεσσήνιοι Φιλίππῳ σύμμαχοι τῷ Ἀμύντου καὶ Μακεδόσιν ἐγένοντο, καὶ τοῦτο σφᾶς λέγουσιν ἀποκωλῦσαι τοῦ συμβάντος τοῖς Ἕλλησιν ἀγῶνος ἐν Χαιρωνείᾳ μὴ μετασχεῖν· οὐ μὴν οὐδὲ τοῖς Ἕλλησιν ἐναντία θέσθαι τὰ ὅπλα ἠθέλησαν.
The Messenians themselves, along with the Argives and Arcadians, held out in the war and sought assistance from the Athenians. The Athenians replied that they would never invade Laconia with them; however, they promised to stand beside them if the Lacedaemonians began hostilities and attacked Messenia. Eventually, the Messenians became allies of Philip, son of Amyntas, and of the Macedonians, and this alliance, they say, prevented them from participating in the battle at Chaeronea between the Greeks. Yet, they refused utterly to bear arms against their fellow Greeks.