Thirukkural 885

உறல்முறையான் உட்பகை தோன்றின் இறல்முறையான் ஏதம் பலவும் தரும்.

Ural muRaiyan uL pagai thonRin iRal muRaiyan etham palavum tharum.

When enmity grows within through improper conduct, death's own way brings many harms. Guard your inner state; for enemies born of your own acts will destroy you.