return the favor

• return the favour (UK)

return the favor (third-person singular simple present returns the favor, present participle returning the favor, simple past and past participle returned the favor)

1. (idiomatic) To do something for someone similar to what they did for you.
   • 2006, David Schmidtz, The Elements of Justice, Cambridge University Press, →ISBN, page 83:

     Having received an unearned windfall, we are in debt. The moral scales are out of balance. The canonical way to restore a measure of balance is to return the favor to our benefactor, as per symmetrical reciprocity. However, the canonical way is not the only way. Another way is to pass the favor on, as per transitive reciprocity.

   • 2010, Scott M. James, An Introduction to Evolutionary Ethics, John Wiley & Sons, →ISBN, page 140:

     Let's say Gertrude shared some of her food with you. This recognition in turn triggers a judgment that you ought to return the favor – that is, you ought to share some of your food with Gertrude when the opportunity arises.