Bhagavatapurana 1.17.16

1.17.16

rājño hi paramo dharmaḥ svadharmasthānupālanam /
śāsato 'nyān yathāśāstram anāpadyutpathān iha //

16. It is indeed the highest act of righteousness on the part of a king to defend the people who are constant in their own duties—since according to shastras he ought to punish those other people who in the absence of calamity go astray (go from the path of righteousness).