From here, Rāma, in his lecture to Vāli, defending his actions, mentions the following two verses from Manu-smṛti. Which exact verses (ch. and verse no.) from Manu is Rāma referring to?
'When kings impose proper punishment on the humans who have sinned, they become sinless and enter heaven as with the pious souls with good deeds.' So says one verse of Manu. [4-18-31]
'Either by punishment or by clemency a thief will be absolved from sin, but the king who does not impose proper punishment will derive the blot of that sin.' So says the other verse of Manu. [4-18-32]