One is expected to return money that another person drops.
Mary is paying for her groceries when she notices a woman walking out the door drop a $50 bill.
Mary wants to make a decision.
Mary picks up the money and hands it back to the woman.
Mary picks up the cash and shoves it into her pocket.
The woman is grateful because now she can still afford all her bills.
The woman can't afford her water bill and has it shut off.