Arrian on kings and falsehood

ἀλλ’ ἐμοὶ Πτολεμαῖός τε καὶ Ἀριστόβουλος πιστότεροι ἔδοξαν ἐς τὴν ἀφήγησιν, ὁ μὲν ὅτι συνεστράτευσε βασιλεῖ Ἀλεξάνδρῳ, Ἀριστόβουλος, Πτολεμαῖοςδὲ πρὸς τῷ ξυστρατεῦσαι ὅτι καὶ αὐτῷ βασιλεῖ ὄντι αἰσχρότερον ἤ τῳ ἄλλῳ ψεύσασθαι ἦν·

Instead, both Ptolemy and Aristoboulos seemed to me to more trustworthy for the narrative: the latter because he campaigned with king Alexander - Aristoboulos - and, the former, Ptolemy, because, in addition to having campaigned in that way, it was more shameful for him to lie than for any other, because he was a king himself.

Arrian, Alexandri Anabasis Prologue 2.