Tirukkural-On Virtue-Pleasing Speech Or Courtesy-Kural 96

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If one seeks always to do good by pleasant speech, Virtues will flourish and sins will disappear.

Fundamental goodness arising from pleasant speech is the basis of virtue, and in the face of such virtue, as before the penance of renunciation, sins cannot stand.

The latter aspect is enunciated in the stanza on 'Thuravu" in Naladiar.
"Thavathin mun nilaadhaam pavam" (51)

All these bring out the many rewards that will accrue in this and the ext life, on those who systematically use, I their human relations, only soft words that are productive of good.