Polybius 12.24.6 (tr. Ian Scott-Kilvert):
men, although they may be present at an event, might just as well
not be there, and likewise may be eye-witnesses yet actually see
nothing; this fact arises from their ignorance and defective
...συμβαίνει διὰ τὴν ἀπειρίαν καὶ κακοκρισίαν πολλοὺς ἐνίοτε καθάπερ εἰ παρόντας τρόπον τινὰ μὴ παρεῖναι καὶ βλέποντας μὴ βλέπειν...
F.W. Walbank in his commentary compares Matthew 13.13 (here in the New International Version):
Though seeing, they do not see;
though hearing, they do not hear or understand.
βλέποντες οὐ βλέπουσιν καὶ ἀκούοντες οὐκ ἀκούουσιν οὐδὲ συνίουσιν.