A sure friend is known in unsure circumstances.
A true friend is a friend when in difficulty
The ape, vilest of beasts, how like to us.
He hath freedom whoso beareth a clean and constant heart within.
Don't ask of your friends what you yourself can do.
O friend unseen, unborn, unknown, Student of our sweet English tongue, I never indulge in poetics - Unless I am down with rheumatics.