Does a divorce occur if I swore an oath of divorce upon my wife that she would not smoke again, then she took a puff from a shisha as a joke and claimed she had forgotten the oath?

If a husband conditions his wife's divorce on her smoking, and divorce occurs due to her performing what he swore upon, this is by agreement of the jurists. If the husband intended by the condition to prevent or threaten, then divorce occurs according to the majority of jurists, while some scholars held that it does not occur. The operative fatwa is the madhhab of the majority. The husband can take back his wife as long as she is within her iddah, provided he has not previously divorced her twice. The wife's forgetfulness, or her doing it in jest, or her smoking little, does not affect the ruling.