You should always return things that aren't yours.
Gordon borrowed Ken's wrench last week and Ken called to ask for it back today.
Gordon wants to decide what to do with the wrench.
Gordon grabs the wrench and brings it right over to Ken.
Gordon decides to keep it for a few more days because he might need it.
Ken is pleased with how quickly Gordon returned the wrench and is now willing to ket him borrow anything he might need in the future because he trusts him.
Ken never lets Gordon borrow anything again because he can't be trusted to return things when asked.