A nod is as good as a wink to a blind horse
A very small hint is enough to convey our meaning. It is not always necessary to say what we want explicitly.
A still tongue makes a wise head
Someone who does not talk much, but listens to other people, probably has experience, knowledge and good judgement.
Barking dogs seldom bite
Don't be afraid of dogs that bark or people that threaten you (say they will do something bad to you) - in both cases they rarely take action.
Better the foot slip than the tongue
It is better to take a bad step in walking than to say the wrong thing in talking. We can do a lot of damage when we say something by mistake. The elliptical nature of this saying may make it difficult to understand. The full version might be something like: "It is better that your foot should slip than that your tongue should slip."
Beware of a silent man and still water
A large expanse of water that is still and does not move is often deep and dangerous. We should be careful of it. In the same way, we should be careful with a person who does not talk much.
Brevity is the soul of wit
The real art of speaking (especially when speaking humorously) is to use as few words as possible.
Dumb dogs are dangerous
People who say little or nothing are more dangerous than people who speak a lot.
Empty vessels make the most noise
Stupid people speak loudest.