Passage 3.15.9
μόνοις δὲ Ἑλλήνων Λακεδαιμονίοις καθέστηκεν Ἥραν ἐπονομάζειν Αἰγοφάγον καὶ αἶγας τῇ θεῷ θύειν. Ἡρακλέα δὲ λέγουσιν ἱδρύσασθαι τὸ ἱερὸν καὶ αἶγας θῦσαι πρῶτον, ὅτι μαχομένῳ οἱ πρὸς Ἱπποκόωντα καὶ τοὺς παῖδας οὐδὲν ἐκ τῆς Ἥρας ἀπήντησεν ἐμπόδιον, ὥσπερ γε ἐπὶ τῶν ἄλλων ἐδόξαζεν ἐναντιοῦσθαί οἱ τὴν θεόν· αἶγας δὲ αὐτὸν θῦσαί φασιν ἱερείων ἀπορήσαντα ἀλλοίων.
The Lacedaemonians alone among the Greeks have established the custom of calling Hera "Aigophagos" (Goat-eater) and of sacrificing goats to the goddess. They say that Heracles founded her sanctuary and was the first to sacrifice goats, because when he fought against Hippocoön and his sons, Hera put no obstacle in his way, although on other occasions he believed the goddess was opposed to him. They say he offered goats because he found no other sacrificial animals at hand.