Passage 4.28.1
κατελθοῦσι δὲ αὐτοῖς κατʼ ἀρχὰς μὲν ἀπὸ Λακεδαιμονίων δεινὸν ἦν οὐδέν· κατεχόμενοι γὰρ οἱ Λακεδαιμόνιοι φόβῳ τῷ Θηβαίων Μεσσήνης τε ἠνείχοντο ἐποικιζομένης καὶ Ἀρκάδων ἐς μίαν ἠθροισμένων πόλιν. ὡς δὲ ὁ πόλεμος ὁ Φωκικός, καλούμενος δὲ ὁ αὐτὸς οὗτος καὶ ἱερός, ἀπήγαγεν ἐκ Πελοποννήσου Θηβαίους, ἀνεθάρρησάν τε οἱ Λακεδαιμόνιοι καὶ τῶν Μεσσηνίων οὐκέτι ἐδύναντο ἀπέχεσθαι.
When the Messenians first returned, they faced no serious threat from the Spartans. For the Spartans, gripped by fear of the Thebans, tolerated both the restoration of Messene and the gathering of the Arcadians into a single city. However, when the Phocian war—also called the Sacred War—drew the Thebans away from the Peloponnese, the Spartans regained their courage and could no longer restrain themselves from acting against the Messenians.