Plutarch, De Iside et Osiride 6

οἶνον δʼ οἱ μὲν ἐν Ἡλίου πόλει θεραπεύοντες τὸν θεὸν οὐκ εἰσφέρουσι τὸ παράπαν εἰς τὸ ἱερόν, ὡς οὐ προσῆκον ἡμέρας πίνειν, τοῦ κυρίου καὶ βασιλέως ἐφορῶντος· οἱ δʼ ἄλλοι χρῶνται μὲν ὀλίγῳ δέ. πολλὰς δʼ ἀοίνους ἁγνείας ἔχουσιν, ἐν αἷς φιλοσοφοῦντες καὶ μανθάνοντες καὶ διδάσκοντες τὰ θεῖα διατελοῦσιν. οἱ δὲ βασιλεῖς καὶ μετρητὸν ἔπινον ἐκ τῶν ἱερῶν γραμμάτων, ὡς Ἑκαταῖος ἱστόρηκεν, ἱερεῖς ὄντες· ἤρξαντο δὲ πίνειν ἀπὸ Ψαμμητίχου, πρότερον δʼ οὐκ ἔπινον οἶνον οὐδʼ ἔσπενδον ὡς φίλιον θεοῖς, ἀλλʼ ὡς αἷμα τῶν πολεμησάντων ποτὲ τοῖς θεοῖς, ἐξ ὧν οἴονται πεσόντων καὶ τῇ γῇ συμμιγέντων ἀμπέλους γενέσθαι· διὸ καὶ τὸ μεθύειν ἔκφρονας ποιεῖν καὶ παραπλῆγας, ἅτε δὴ τῶν προγόνων τοῦ αἵματος ἐμπιπλαμένους. ταῦτα μὲν οὖν Εὔδοξος ἐν τῇ δευτέρᾳ τῆς περιόδου λέγεσθαί φησιν οὕτως ὑπὸ τῶν ἱερέων.

As for wine, those who serve the god in Heliopolis bring none at all into the shrine, since they feel that it is not seemly to drink in the day-time while their Loi’d and King is looking upon them. The others use wine, but in great moderation. They have many periods of holy living when wine is prohibited, and in these they spend their time exclusively in studying, learning, and teaching religious matters. Their kings also were wont to drink a limited quantity prescribed by the sacred writings, as Hecataeus has recorded; and the kings are priests. The beginning of their drinking dates from the reign of Psammetichus; before that they did not drink wine nor use it in libation as something dear to the gods, thinking it to be the blood of those who had once battled against the gods, and from whom, when they had fallen and had become commingled with the earth, they believed vines to have sprung. This is the reason why drunkenness drives men out of their senses and crazes them, inasmuch as they are then filled with the blood of their forbears. These tales Eudoxus says in the second book of his World Travels are thus related by the priests.