I couldn't ask you to do that

I couldn't ask you to do that.

That is a very kind offer, but I would not ask you to do it. (This is not a refusal of the offer.) Sally: Look, if you want, I'll drive you to the airport. Mary: Oh, Sally. I couldn't ask you to do that. BUI: I'll lend you enough money to get you through the week. Sally: I couldn't ask you to do that.
See also: ask, that