Tirukkural-On Virtue-Not Coveting Another's Wife-Kural-150

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Even if one does not practise any other virtue and is a sinner,If were best that he does not trespass into the home-life of his neighbour.

Among those who stray from the path of right conduct and commit sins, there is none so despicable as the one who lusts after the neighbour's wife. Religion as well as social order are offended by such a man's conduct, which by other deviance will only affect him personally.