I'm not going to pay back the money I owe to my friend for rent.
Why won't you pay your friend back?
My friend doesn't really do anything and doesn't deserve to be paid back.
I know your friend is probably causing you some frustration, but you have to pay back money you've borrowed from others. This is money that you owe for rent and you made an agreement to pay that same money.
Fine, whatever, and I'll show you.
I'm not sure exactly what you mean, but I hope that you are willing to pay your friend back, because this is indeed a true legal obligation on your part.  There is no need for you to show me proof, I just need you to understand that you should honor your obligations, even when others are being disagreeable.