Passage 1.7.3
Μάγας δὲ ἤδη γυναῖκα ἔχων Ἀπάμην Ἀντιόχου τοῦ Σελεύκου θυγατέρα, ἔπεισεν Ἀντίοχον παραβάντα ἃς ὁ πατήρ οἱ Σέλευκος ἐποιήσατο συνθήκας πρὸς Πτολεμαῖον, ἐλαύνειν ἐπʼ Αἴγυπτον. ὡρμημένου δὲ Ἀντιόχου στρατεύειν, Πτολεμαῖος διέπεμψεν ἐς ἅπαντας ὧν ἦρχεν Ἀντίοχος, τοῖς μὲν ἀσθενεστέροις λῃστὰς κατατρέχειν τὴν γῆν, οἳ δὲ ἦσαν δυνατώτεροι στρατιᾷ κατεῖργεν, ὥστε Ἀντιόχῳ μήποτε ἐγγενέσθαι στρατεύειν ἐπʼ Αἴγυπτον. οὗτος ὁ Πτολεμαῖος καὶ πρότερον εἴρηταί μοι ὡς ναυτικὸν ἔστειλεν ἐς τὴν Ἀθηναίων συμμαχίαν ἐπʼ Ἀντίγονον καὶ Μακεδόνας· ἀλλὰ γὰρ ἀπʼ αὐτοῦ οὐδὲν μέγα ἐγένετο ἐς σωτηρίαν Ἀθηναίοις. οἱ δέ οἱ παῖδες ἐγένοντο ἐξ Ἀρσινόης, οὐ τῆς ἀδελφῆς, Λυσιμάχου δὲ θυγατρός· τὴν δέ οἱ συνοικήσασαν ἀδελφὴν κατέλαβεν ἔτι πρότερον ἀποθανεῖν ἄπαιδα, καὶ νομός ἐστιν ἀπʼ αὐτῆς Ἀρσινοΐτης Αἰγυπτίοις.
Now, Magas, having already married Apame, the daughter of Antiochus son of Seleucus, persuaded Antiochus to break the treaty his father Seleucus had made with Ptolemy and to march against Egypt. But when Antiochus prepared to invade, Ptolemy dispatched forces throughout all the territories under Antiochus' rule; against the weaker lands he sent raiders who devastated the country, while against those stronger he brought armies to attack, so that Antiochus was never able even to begin his campaign against Egypt. This Ptolemy, as I mentioned earlier, had once sent a naval force to assist Athens in their alliance against Antigonus and the Macedonians, though from him nothing significant resulted in the salvation of the Athenians. His children were born to him from Arsinoë, not Arsinoë his sister, but the daughter of Lysimachus. His sister, whom he had also married, had previously died childless, and an Egyptian district, the Arsinoite nome, is named for her.