Passage 4.19.3
ἔθυσε δὲ καὶ τῷ Διὶ τῷ Ἰθωμάτᾳ τὴν θυσίαν ἣν ἑκατομφόνια ὀνομάζουσιν. αὕτη δὲ καθεστήκει μὲν ἐκ παλαιοτάτου, θύειν δὲ αὐτὴν Μεσσηνίων ἐνομίζετο ὁπόσοι πολεμίους ἄνδρας κατεργάσαιντο ἑκατόν. Ἀριστομένει δέ, ὅτε ἐπὶ Κάπρου σήματι ἐμαχέσατο, θύσαντι ἑκατομφόνια πρῶτον, δεύτερα ἤδη θῦσαι καὶ ὁ ἐν τῇ νυκτὶ τῶν Κορινθίων παρέσχε φόνος. τοῦτον μὲν δὴ λέγουσι καὶ ἐπὶ ταῖς ὕστερον θῦσαι καταδρομαῖς θυσίαν τρίτην, Λακεδαιμόνιοι δὲ---ἐπῄει γὰρ
He sacrificed also to Zeus Ithomatas the offering they call "Hekatomphonia" (the sacrifice for one hundred slain). This practice was very anciently established, and it was customary among the Messenians to offer it whenever they had slain one hundred enemies. Aristomenes first offered this sacrifice after he had fought at the tomb of Kapros; a second occasion was provided for him by the slaughter of the Corinthians during the night. They say he also performed this sacrifice a third time after his subsequent attacks; but the Lacedaemonians—for he was advancing toward them—