Speak well of your friend, of your enemy say nothing.

I sometimes think that 'friend' is just a word I use for all the people I haven't murdered yet.

Tell nothing to thy friend which thy enemy may not know

If you're going to live by the river, make friends with the crocodile

Not all things have to be scrutinized, nor all friends tested, not all enemies exposed and denounced

When you are without friends, the next best thing is an enemy who knows you well.