Why do we say "Think before you speak"?

Background:

The earliest known reference to this expression in broadly its modern form is found in R. Edgeworth's Sermons (1557): "Thinke well and thou shalt speak well."

It's safe to assume that Roger Edgeworth was paraphrasing a Biblical quote--and there are plenty to choose from, including:

All who are prudent act with knowledge, but fools expose their folly. (Proverbs 13:16)

My dear brothers and sisters, take note of this: Everyone should be quick to listen, slow to speak and slow to become angry... (James 1:19)

Do you see someone who speaks in haste? There is more hope for a fool than for them.. (Proverbs 29:20)

(New International Version)

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