Correction: The Wikisource transcription I used appears to omit part of the passage.
The printed Loeb edition (Paton, 1922) reads:
"...he who kills a thief or adulterer is guiltless, and the slayer of a traitor or tyrant everywhere meets with honour and distinction."
"...ὁ μὲν τὸν κλέπτην ἢ μοιχὸν ἀποκτείνας ἀθῷός ἐστιν, ὁ δὲ τὸν προδότην ἢ τύραννον τιμῶν καὶ προεδρίας τυγχάνει παρὰ πᾶσιν."
— Polybius, Histories II.56.15–16 (Loeb Classical Library, Vol. I, trans. W. R. Paton, 1922)