Tirukkural-On Virtue-On Self Restraint-Kural 127

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Whatever else is left unguarded, one should restrain the tongue,For a wagging tongue could give immense trouble.

Control of the tongue is more important than that of any of the other senses in that failure to do so can result in immense harm to others and ultimately to oneself. Cato too said very much the same, when he enjoined that the first virtue is 'to restrain the tongue'.

The idea here is certainly not that one may relax control in all other respects. The injunction is only based on relative harm done and is meant to emphasise the danger of careless and licentious speech. Biblical support for these lines could be had in the following lines:

'The wicked are snared by the transgression of their lips'.

(Proverbs 12:13)

Silapadikaram and Jeevaka Chinthamani have used this idea thus:
Kaavaa naavir kanakanum visayanum

(Silap. 26 : 159)