Is an oath considered binding if it was uttered unintentionally and then the intention to make it binding occurred after its utterance?

The cure for obsessive whispers (waswas) is to turn away from them, ignore them, and pay them no mind. The intention after uttering an oath has no effect. As long as the oath was made without the intention of being a binding oath, it is a vain oath (laghw al-yamin) for which no expiation is due.