οὐκ ἔστ' ἀκριβὲς οὐδὲν εἰς εὐανδρίαν

From LSJ

ψευδόμενος οὐδεὶς λανθάνει πολὺν χρόνον → nobody lies for a long time without being discovered

Source

English > Greek (Woodhouse Quotes Reversed)

there is no sure mark to show true manhood