Regardless of the religion or situation that brought the person to breaking an oath, I'd immediately be fascinated. I'd want to know pretty much every detail that lead to the break, what kind of break it was and so on. I am a ridiculously curious person though. Do not leave me in an area with personal information for too long unattended and don't bring up something you don't really want to talk about with me. I can draw back from my curiosity when a person gives clear signals they don't want to talk or it's obvious that I'd be way too intrusive but it's really not my strong suit.
Other emotional reactions would come after I'd learned more. Generally speaking I'd probably be sympathetic or think that the person I was talking to was rash/dumb/uninformed for either making unobtainable oaths or for breaking them so quickly. I could feel any range of other emotions startled, welcoming, sad, worried all come to mind. I don't think I'd be angry or offended though, I mean that's between that person and those god(s/esses).
I might be wary of that person if they had broken a ton of oaths or this seemed to be some kind of habit, just because they might not be very reliable. It's not a crime to be rash or flaky but it would be a major inconvenience in my life, so I'd probably keep some distance with a person who acted that way.
