Passage 9.33.4
ἔστι δὲ ἐν τῇ Ἁλιαρτίᾳ ποταμὸς Λόφις. λέγεται δὲ τῆς χώρας αὐχμηρᾶς οὔσης τὸ ἐξ ἀρχῆς καὶ ὕδατος οὐκ ὄντος ἐν αὐτῇ ἄνδρα τῶν δυναστευόντων ἐλθόντα ἐς Δελφοὺς ἐπερέσθαι τρόπον ὅντινα ὕδωρ εὑρήσουσιν ἐν τῇ γῇ· τὴν δὲ Πυθίαν προστάσσειν, ὃς ἂν ἐπανήκοντι ἐς Ἁλίαρτον ἐντύχῃ οἱ πρὸ τῶν ἄλλων, τούτου δεῖν φονέα γενέσθαι αὐτόν. ἐντυχεῖν τε δὴ αὐτῷ παραγενομένῳ τὸν υἱὸν Λόφιν καὶ τὸν οὐ μελλήσαντα τῷ ξίφει τὸν νεανίσκον παῖσαι· καὶ τὸν μὲν ἔτι ἔμπνουν περιθεῖν, ὅπου δὲ ῥυῆναι τὸ αἷμα, ὕδωρ ἐντεῦθεν ἀνεῖναι τὴν γῆν. ἐπὶ τούτῳ μὲν ὁ ποταμὸς καλεῖται Λόφις·
In Haliartia there is a river called Lophis. It is said that originally, as the territory was parched and lacking water, one of the ruling men went to Delphi and inquired how they might find water in the region. The Pythian priestess instructed him that he must kill the first person he met upon returning to Haliartus. On his return, he first encountered his own son, Lophis. Without hesitation, he struck the youth with his sword. The wounded son, still breathing, began to run about, and wherever the blood flowed, water sprang forth from the ground. For this reason, the river is named Lophis.