Asking for money

If your man asked you for money would you ask him what it's for out of curiosity or do you feel it's none of your business what he needs it for just as long as he pays you back when he says he would ?? My guy and I look out occasionally for one another. When I don't have he gets for me. When he doesn't have I get for him. Normally stuff like food or whatever. So I know he gets paid tomorrow. He asked me for $80. I don't mind giving it to him because I know for a fact he will pay me back but I just asked out of curiosity what he needed the $80 for. He doesn't normally ask me for such a large sum of money. It's normally something small like $30, or $40 and he'll normally say it's for something like gas or to get groceries. I let him borrow the money but he was heated with me because I asked what he needed $80 for. He told me that I shouldn't question him about things like that because he doesn't question me when I ask to borrow money from him. I wasn't trying to monitor him because it's not like he has a bad habit or anything. I just was curious to know and he just got all pissed off with me. Was I wrong because if so , I will rightfully apologize but I didn't feel like I was wrong asking why he wanted to borrow $80 of my money until tomorrow ?