Wise men speak because they have something to say; Fools because they have to say something.
Speak not at all, in any wise, till you have somewhat to speak; care not for the reward of your speaking, but simply and with undivided mind for the truth of your speaking.
I will begin to speak when I have that to say which had not better be unsaid.
Marcus Porcius Cato Uticensis
Say not always what you know, but always know what you say.
It is better wither to be silent, or to say things of more value than silence. Sooner throw a pearl at hazard than an idle or useless word; and do not say a little in many words, but a great deal in a few.
He that hath knowledge spareth his words.
No one can take less pains than to hold his tongue. Hear much, and speak little; for the tongue is the instrument of the greatest good and greatest evil that is done in the world.
I've always been a guy who's reserved my words for the right time.
There is a better thing than the great man who is always speaking, and that is the great man who only speaks when he has a great word to say.
I'm not a talker unless I really feel I have to say something.
Put a bridle on thy tongue; set a guard before thy lips, lest the words of thine own mouth destroy thy peace... on much speaking cometh repentance, but in silence is safety.
The wisdom of silence is a great asset.
On the power of the Speaker:
Preach not because you have to say something, but because you have something to say.
I really don't have anything urgent to say, and I think you shouldn't write unless you have something urgent to say. Sometimes that troubles me, and sometimes I don't really care.