Clarity of thought is a must for brevity in speech.

Against the censurers of brevity. - Something said briefly can be the fruit of much long thought: but the reader who is a novice in this field, and has as yet reflected on it not at all, sees in everything said briefly something embryonic, not without censuring the author for having served him up such immature and unripened fare.

A speck of ire can
blaze a fire; the fate of war can
be sealed with a dart,
a butterfly flapping its wings
may turn the tide miles apart!

Brevity is the best recommendation of speech, whether in a senator or an orator.

Brevity is a great charm of eloquence.

In labouring to be concise, I become obscure.