Passage 4.15.6
ἐγένετο δὲ καὶ Λακεδαιμονίοις μάντευμα ἐκ Δελφῶν τὸν Ἀθηναῖον ἐπάγεσθαι σύμβουλον. ἀποστέλλουσιν οὖν παρὰ τοὺς Ἀθηναίους τόν τε χρησμὸν ἀπαγγελοῦντας καὶ ἄνδρα αἰτοῦντας παραινέσοντα ἃ χρή σφισιν. Ἀθηναῖοι δὲ οὐδέτερα θέλοντες, οὔτε Λακεδαιμονίους ἄνευ μεγάλων κινδύνων προσλαβεῖν μοῖραν τῶν ἐν Πελοποννήσῳ τὴν ἀρίστην οὔτε αὐτοὶ παρακοῦσαι τοῦ θεοῦ, πρὸς ταῦτα ἐξευρίσκουσι· καὶ ἦν γὰρ Τυρταῖος διδάσκαλος γραμμάτων νοῦν τε ἥκιστα ἔχειν δοκῶν καὶ τὸν ἕτερον τῶν ποδῶν χωλός, τοῦτον ἀποστέλλουσιν ἐς Σπάρτην. ὁ δὲ ἀφικόμενος ἰδίᾳ τε τοῖς ἐν τέλει καὶ συνάγων ὁπόσους τύχοι καὶ τὰ ἐλεγεῖα καὶ τὰ ἔπη σφίσι τὰ ἀνάπαιστα ᾖδεν.
There came also to the Lacedaemonians an oracle from Delphi, instructing them to take an Athenian as adviser. They therefore sent envoys to Athens, to announce the oracle and request a man who would counsel them as to what they should do. But the Athenians, unwilling either that the Lacedaemonians without great trouble should easily acquire the finest portion of the Peloponnese or themselves openly disobey the god, devised the following plan. There was at that time among them a teacher of letters named Tyrtaeus, who appeared to have little intelligence and was lame in one foot; this man they dispatched to Sparta. When Tyrtaeus arrived, he recited privately to the leaders and publicly, to whoever happened to gather around, his elegiac verses and his anapaestic poems.