DEAR MISS MANNERS: I asked a neighbor/friend if I could "borrow" an egg. He was happy to oblige. I asked if he liked banana muffins, and he said that he did.
I just got back from delivering him a couple of banana muffins, fresh from the oven. Do I still owe him an egg?
GENTLE READER: Yes, because the egg was compromised. It was not returned in its original condition, having first been beaten and then baked. Miss Manners trusts that should you borrow a lawnmower, you won't return it in a similar state.
What you owe him now is the same sort of neighborliness when he is in need.