courtesy costs nothing

courtesy costs nothing

proverb It is easy to be respectful. You don't have to be their best friends, but you could at least say hi to them—courtesy costs nothing.
See also: cost, courtesy, nothing
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
See also:
References in classic literature ?
It is a proverb that 'courtesy costs nothing'; but calculation might come to value love for its profit.
Please, Track 2000, respect costs nothing, courtesy costs nothing. Do not bite the hand that feeds you or you may come to regret it.
My first headmaster told me "courtesy costs nothing" - a fairly sage maxim.
Common courtesy costs nothing," says Swinton director Chris Collings.
The thing I can't understand is why the warden didn't call him through the open door - it would have been courteous to do so - and there's my answer - courtesy costs nothing.