Across cultures there are many different ways of telling people to watch what they say. After hunting out a correction to
"The walls have ears" I found loads more proverbs running across the same ideas
Speaker orientated
Had the pheasant not screamed, it wouldn't have been shot. (Japanese)
If the bird had not sung, it wouldn't have been shot. (Japanese)
Below the tongue, there is an axe hidden. (Korean)
The talker talks and causes death in his family. (Haya)
More than one war has been caused by a single word. (Arabic)
Don't let your tongue say what your head may pay for. (Italian)
He who holds his tongue will save his head. (Turkish)
A knife wound heals: a wound caused by words does not. (Turkish)
Words are like spears, once they leave your lips they never come back. (Yoruba)
A word and a stone let go cannot be recalled. (American)
Where there is a surfeit of words there is a famine of intelligence. (Marathi)
A fool is like the big drum that beats fast but does not realise its hollowness. (Malay)
Empty vessels make the most sound. (English)
Empty vessels make the most noise. (Turkish)
Rippling water shows lack of depth. (Indonesian)
In the shoal ripple the light waves. (Japanese)
When he brayed, the jackass showed he was not a lion. (Egypt)
From opening the mouth, seven ills may ensue. (Hindustani)
The talker will lead the dog to the meat market. (Buganda)
The body pays for a slip of the foot, and gold pays for a slip of the tongue. (Malay)
You will hate a beautiful song if you sing it often. (Korean)
Teach thy tongue to say, "I do not know." - (Hebrew)
The word that leaves your mouth leaves your control. (Somali)
Once out of the throat it spreads over the world. (Hindustani)
Before you speak, turn your tongue seven times in your mouth. (Yoruba)
Turn each word seven times in your mouth before you speak. (Moroccan Arabic)
What lies in the heart of a man can only be known if it passes the throat. (Yoruba)
When you are not asked, do not speak. (Maltese)
If you have a windfall, shut the door and dance unseen. (South Africa)
Keep the tongue in your mouth a prisoner. (Turkish))
What a man suffers is the punishment of his tongue. (Turkish)
Let the mouth be the trap of your words. (Zambia)
The tongue is more to be feared than the sword. (Japanese)
Many speak much who cannot speak well. (American)
Better the foot slip than the tongue. (American)
To lock up mischief, keep your mouth closed. (Chinese)
The less one thinks, the more one speaks. (French)
Words often do worse than blows. (German)
Hearer orientated
Silence surpasses speech - (Japanese)
Silence was never written down - (Italian)
A silent mouth is sweet to hear - (Irish)
Speech is often repented, silence never - (Danish)
Silence is also speech - (Yiddish)
"Walls have ears". (English)
"Walls have ears". (Chinese)
"Walls have ears". (Korean)
Walls have ears, paper sliding doors have eyes. (Japanese)
Walls have ears, bottles have mouths. (Japanese)
Walls have ears, and little pots too. (South African)
The walls have mice, and the mice have ears. (Persian)
Windows have ears; doors have holes. (Thai)
When words are spoken there also words are heard. (Yoruba)
Give your ear to words but do not give your words to ears. (Hindustani)
A statement let loose cannot be caught by four galloping horses. (Japanese)
No sooner have you spoken than what you have said becomes the property of another. (Hindustani)
Sources include -
http://www.deproverbio.com/DPjournal/DP,1,2,95/SPEECH_SILENCE_PROVERBS.html
http://mansioningles.metropoli2000.net/acti13.htm
If anyone writes the origin of these proverbs up, /msg me and I'll hard-link your write up into them