The exact original video behind this clip is not widely documented, which is common for short Arabic reaction sounds shared as standalone audio on soundboard sites. The phrase qul qasam itself is everyday Arabic for say I swear, so its humour comes from the familiar way people demand proof during an argument or a joke. Online it circulates mainly as a quick reaction for disbelief, often reused in short videos, memes and group chats where a single spoken line can carry the whole response.