Isocrates Quote

Always when you are about to say anything, first weigh it in your mind; for with many the tongue outruns the thought. Let there be but two occasions for speech — when the subject is one which you thoroughly know and when it one on which you are compelled to speak. On these occasions alone is speech better than silence; on all others, it is better to be silent than to speak.

Verse 41. - To Demonicus