知る者は言わず言う者は知らずの英語

He who knows, does not speak. He who speaks, does not know.

I do not mind what people say.

I don't mind what people say.

He gives no heed to advice or warning.

You cannot judge a person if you don't know him well.

Some people can't admit they're wrong.

There are people who can't admit they're wrong.

Kindness is thrown away upon ungrateful people.

one cannot say such things lightly

a refusal to recognize someone you know

Who lives without folly is not so wise as he thinks.

a professed liar

He is a perfect stranger to me―a complete stranger to me.

You can't judge a person if you don't know him well.

Don't judge a man by what he has.

People will be blind to their own interests.

That comes of neglecting my advice.

to caution a person for their bad behavior

You should not condemn a person unheard.

No one likes being thought a fool.

Don't make a fool of me.

One who does not know a foreign language does not know his own―（古文体にては）―He who knows not a foreign language, knows not his own.

Never speak ill of the absent

“Nil nisi bonum.”【イディオム・格言的】

It is mean of him to expose others' faults.

You should not speak ill of people.

exhibiting contempt for his unlettered companions

I'll teach you to meddle in my affairs.

secret acts of charity

in speaking or writing, to be off the main point or theme