AITA I won't pay back my friend on a bet.

So last Friday me and my friend bet on Tuesday (Today) being cancelled and I said no it won't be. Well I was proved wrong and I didn't think the bet serious we just said bet we'll bet $100. So now my friend actually expects money and if I can't pay back we won't be friends and that he'll block me on all social media. These are messages he sent me on snap. Not sure what to do I can't consult him because he's genuinely mad I think. I asked to call him to see if he was just joking but he always kept messaging "No!". So I don't know what do and I'm curious if I'm the asshole or not because I don't think I may be if you disagree let me know.