Polly advises Jerry to follow what's called The Golden Rule: Do unto others as you would have them do unto you. Polly tells her husband about poor old Dinah Brown. She's just received a letter informing her of bad news: her mother is dangerously ill. Naturally, Dinah wants to go off and visit her sick mother, but as she lives ten miles away, it would take her a long time to get there. Even if she took the train, she'd still have to walk some considerable distance. Polly doesn't think that would be fair given Dinah's weakened condition.
So she asks Jerry if it'll be alright for him to take Dinah in his cab. At first, Jerry's quite reluctant; Sunday's a very special day to this deeply religious man, and driving Dinah all the way to her mother's house will take the better part of half a day. That's when Polly reminds Jerry of The Golden Rule. As Polly's managed to convince Jerry that he won't break the Sabbath by driving Dinah to her mother's house, he agrees to take her.