Passage 8.47.5
Τεγεάταις δέ ἐστι καὶ ἄλλο ἱερὸν Ἀθηνᾶς Πολιάτιδος, ἑκάστου δὲ ἅπαξ ἔτους ἱερεὺς ἐς αὐτὸ ἔσεισι· τοῦτο Ἔρυμα τὸ ἱερὸν ὀνομάζουσι, λέγοντες ὡς Κηφεῖ τῷ Ἀλέου γένοιτο δωρεὰ παρὰ Ἀθηνᾶς ἀνάλωτον ἐς τὸν πάντα χρόνον εἶναι Τεγέαν, καὶ αὐτῷ φασιν ἐς φυλακὴν τῆς πόλεως ἀποτεμοῦσαν τὴν θεὸν δοῦναι τριχῶν τῶν Μεδούσης.
The Tegeans have also another sanctuary of Athena Polias, into which the priest enters only once in each year. They call this shrine the Eryma ("Defense"), saying that Athena gave it as a gift to Cepheus, son of Aleus, that Tegea might remain unconquered for all time. They say that the goddess, having cut off hairs from the head of Medusa, gave them to him as a protection for the city.