Ξάνθος δὲ ἐν τοῖς ἐπιγραφομένοις Μαγικοῖς †, “μίγνυνται δὲ”, φησὶν, “οἱ μάγοι μητράσι καὶ θυγατράσι· καὶ ἀδελφαῖς μίγνυσθαι θεμιτὸν εἶναι· κοινάς τε εἶναι τὰς γυναῖκας, οὐ βίᾳ καὶ λάθρᾳ, ἀλλὰ συναινούντων ἀμφοτέρων, ὅταν θέλῃ γῆμαι ὁ ἕτερος τὴν τοῦ ἑτέρου.
(Clement of Alexandria Strom. 3.2.11 = Xanthus Lydus, FGH 765 F31)

Xanthus says in his book entitled Magica “The mages have sex with their mothers,” and he says that it is customary for them to have sex with their daughters and sisters too, and that the women were held in common. Such unions were not forced or secret, but were readily consented to by both parties, whenever one man wanted to marry the woman of another. (tr. Daniel Ogden)