The line crossed
Taking or withholding someone else’s property for your own gain.
Commandment 8 · Do not steal

You find a wallet after an event. There is enough cash inside to solve a problem you have not told anyone about. Your friend looks up at a security camera. “Probably fake,” they say. You realise your next choice may depend on whether you think anyone can see.
Thou shalt not steal.Exodus 20:15 · King James Version
There is a cost behind every answer. Choose one to examine it.
Taking or withholding someone else’s property for your own gain.
Returning the full wallet without demanding a private reward.
Need and opportunity can explain temptation. Neither transfers ownership.
Write two honest ways to address the money problem. Which trusted person could help you pursue one of them?